It's my understanding that yes, you will get a bit of an increase, but the reason for upgrading is so you can push all of your hardware a little further and not have your RAM be the deciding factor.
You might not be able to run as tight timings as you have currently, but you'll have more headroom to get a higher overclock.
From what i've been reading regarding memory lately is the Buffalo Firesticks and as was stated, the Super Talent brands are the "In Things". That is, if you can find anywhere that has them in stock. I love my Patriot sticks, but I really have to loosen the timings to get them stable at higher speeds & they do get really hot.
You have a pretty good budget to get a top of the line kit. I'm thinking OCZ or Corsair would be your best bet. I've also noticed that RAM pricing is in a downward trend for the moment.. maybe stick it out for a bit & see what becomes. Perhaps check pricewatch daily & see what the market is doing... gotta love the Green arrows :D
http://www.pricewatch.com/memory/
(if you do decide to buy from any of the dealers listed on pricewatch, read the feedback first!!!!!)