You don't have to invest in penny stocks to find low priced-stocks that represent good values. There are plenty of companies that trade under $20 that have exceptional growth potential. You might even call the price point the sweet spot of investing.

We asked three Motley Fool contributors to identify top stocks under $20 that investors could buy right now to generate exceptional returns. Below, they discuss Crocs (NASDAQ:CROX), Sirius XM Holdings (NASDAQ:SIRI), and Wendy's (NASDAQ:WEN).

A pair of bright green casual clogs

Image source: Getty Images.

Getting back on the right foot

Dan Caplinger (Crocs): Many apparel and footwear companies go through a brief period of popularity, establishing a fashion craze that quickly flames out. Crocs appeared to be exactly that sort of company, with its now-famous sandals with holes having created a huge business that sent the stock soaring in 2007. Yet the financial crisis threw the footwear specialist for a loop, and even after a modest recovery in 2010 and 2011, Crocs struggled to put together a lasting turnaround strategy. By last year, shares had lost 90% of their value from the 2007 peak.

Now, though, Crocs shares have nearly tripled from those low levels in 2017, and investors are more convinced that the company has a viable vision for the future. Profits have returned, and store closings have brought Crocs' retail operations closer to the appropriate size. Moves to control expenses have paid off with substantial profit growth in recent quarters, and with a simplified production model and rising influence of e-commerce sales, the company has regained its footing in a challenging industry.

Crocs still has a long way to go to maintain its relevance in the fickle world of fashion, but by maintaining a smart balance between wholesale distribution and direct-to-consumer internet-based sales, it might not have a share price below $20 for very much longer.

Long live radio

Daniel Miller (Sirius XM): One might think that Sirius XM was doomed once podcasts became a common way to digest news and information, and that consumers have many options beyond radio for consuming music these days. But Sirius XM continues to chug along adding to its subscriber base, fueling a consistent rise in revenue and stock price:

SIRI Chart

SIRI data by YCharts.

In fact, the satellite radio provider just reported a better-than-expected second quarter and raised many full-year guidance figures higher. Sirius XM exited the second quarter adding 483,000 more self-pay subscribers than it had at the end of the first quarter, bringing its total subscriber count to more than 33.5 million. Furthermore, the company's second-quarter churn checked in at a record low of 1.6% -- so not only is Sirius XM adding more members, but they're sticking around.

One analyst, Credit Suisse's Doug Mitchelson, initiated coverage of Sirius XM in July; he set a price target of $8.50, a premium to its $6.88 price at close on Aug. 7, saying the company's aggressive share-repurchase program would help drive its stock higher.

Although it has posted strong results over the years, Sirius will still have to find, acquire, and develop the best music, entertainment, sports, and comedy programming in radio -- such as its recent deal with Netflix for a new comedy channel -- because the competition for original content and talent is heavy. So far, Sirius has been able to do that. For investors who believe it will continue to develop top radio programming, it's a top stock under $20.

A Wendy's restaurant

Image source: Wendy's.

Take a bite out of Wendy's

Rich Duprey (Wendy's): It's been almost a decade since Wendy's stock last saw $20 a share, but despite the continuing battle between it, Burger King, and McDonald's (NYSE:MCD), there remains good reason to think Wendy's could break through that level and grow much more.

The burger wars are nothing new, though over the past few years they seem to be even more competitive, as each player tries to outdo the others in presenting itself as the best restaurant for a value-priced meal. Wendy's, however, has largely been able to play that game better, and has consistently seen same-store sales grow. In its first-quarter earnings report, it noted that comps have grown for 21 consecutive quarters.

McDonald's has had an especially tough time achieving consistent growth; when comps have come in higher, it's been more because it raised prices or people were ordering more expensive items, rather than getting more customers in the door.

Perhaps more importantly, Wendy's has been able to continuously increase restaurant volumes, with average North American unit sales reaching $1.6 million last year, a company record.

Recently an analyst downgraded Wendy's stock from buy to neutral because he believes that having lapped its $0.50 Frosty promotion from a year ago, the chain will struggle, particularly since McDonald's and Burger King are expected to get even more promotional than they already are.

That would suggest Wendy's is the one to beat, but over the years the quick-serve burger chain has proved itself up to the task. Year to date the stock is up only 2%, while down 8% from its 52-week highs. It would be a mistake to count out Wendy's ability to respond if necessary, and its under-$20 price point makes it an attractive stock to buy.