Hey man, I'd recommend staying away from the SRC, just because there isn't really much in the way of aftermarket support for it. i.e. RA-Tech and other companies haven't made many replacement/upgrade parts for them...if any.
If you're looking for an AK GBBR, then the rest of the guys on here have got it right. Wait for the WE TECH AK!!!!!! The GHK AK74s out there aren't worth their weight in dung, and unless you want to drop money into upgrading your hop up, nozzle and maybe even the bolt into RA-Tech parts, then they're not worth it for gaming. Plus, other parts on the gun will break in time and you'll have to source AK drop in kits for those extra parts since no body makes them. (the kits are almost impossible to find now, only 3 left on Airsoftdepot and very few elsewhere online)
The Armalites are your best bet and WE Tech takes the cake...for now. The WE Tech M4s have quite a few upgrade parts and so many people have them that it shouldn't be hard to find what you're looking for. Plus, you can get the NPAS system that will allow you to dial up your FPS or down as you see fit. You can even drop it under 300 FPS if you really want to. SUPER BONUS, you can buy the CO2 ready version, so you don't have to always use propane. CO2 is great for those colder days, unless you spray and pray.
The WA platform is great too in my opinion, but a bit more expensive. You do however, have the option of buying cheaper Chinese parts, so it might not break the bank like a WE Tech can when you upgrade it. If you've got the dough though, WA GBBRs are great cause makers like Bomber, Viper, Inokatsu and Prime make much nicer receivers than WE Tech IMOP.
KJWs are great, and quite reliable, but suffer from a similar problem as the SRC AK, i.e. very little replacement/upgrade options. Plus, they're the least similar to a real AR, so it's not as cool when you tear it down.
So, in conclusion, until WE Tech comes out with their entry into the AK market, I'd agree with most on here and stick to Armalite models for now, or if you want a smaller platform, the WE PDW is a decent pick too.