Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Big Board operator NYSE Euronext (NYSE: NYX) are living large today, jumping as much as 16.5% on many times the average trading volume.

So what: A fresh buyout proposal from NASDAQ OMX (Nasdaq: NDAQ) and IntercontinentalExchange (NYSE: ICE) has come along to trump the existing offer by German exchange Deutsche Borse. NYSE's board is reviewing the offer and has yet to accept or reject it.

Now what: The NASDAQ/ICE offer of $42.50 per share is actually 19% higher than the old deal, and there's a fair amount of spread between the bid and the current share price. Whoever walks away with the big prize will have created a truly massive, trans-Atlantic stock exchange -- assuming that American and European regulators allow it. That arbitrage opportunity rests on pure uncertainty about the outcome.

Interested in more info on NYSE Euronext? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. NYSE Euronext is a Motley Fool Rule Breakers pick. The Fool owns shares of Nasdaq OMX Group. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.