I'm running around 380 FPS on my M4 and don't see or feel the need to upgrade to 400, that 10-15 FPS gain doesn't really matter too much in my eyes and I'm 100% safe in regards to not hitting the upper limit.
As far as style goes, AR15 and AK are your best bets, try going full size if you're a larger guy or maybe a slightly shorter size if you're smaller or a medium size. ie. if you're 4'9" don't get a full size M16 and if you're 6'11" having a puny MP5 probably won't work for you.
As far as brands go, TM is your standard. However you can go with ones like CA, G&P, VFC, KA, Real Sword, etc.
As far as the SRC goes, and what I've read, it's on par with your higher tier brands however since you have access to the classifieds anyways it doesn't hurt to take a peruse through the classifieds and shop around, see something you like and maybe buy full metal goodness if that takes your fancy.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE