If money is an issue, then follow the above suggestions about souping up your MTBs. If you can afford it then my advice, FWIW, is to keep the MTBs for backup and go shopping! "Performance"-type hybrids like the Trek FX series won't be too much of a departure from what you're already used to, but you may also want to check out some more road-type of bikes. Your choices are somewhat limited in the price range you mentioned, but many LBSs often have discontinued, previous year's, or even used models for sale. If you do test ride a road bike (BTW cyclocross and touring bikes can make great commuters) and you find that you like it, reasonably-priced models can also be found online from places like Bikes Direct (but personally I prefer my LBS):

http://www.bikesdirect.com/products/..._cross_cx3.htm

http://www.bikesdirect.com/products/windsor/tourist.htm