DO NOT GET THE AIM SVD GBBR!!!! Its a money pit..
The Mk1/Mk2 carbine has a very hard trigger pull, accuracy is poo, and its hard to get parts for. Of course like most rifles, if you have money to invest into it, it can be a cool rifle though. I had one back in 2006 and I liked it, but couldnt use it much.
I suggest a Bar10 or something like that. Right now in our commerce section in the "Web deals" there is a link to a boneyard Bar10 on Ebay for $35! Whatever the problem it has... It CAN be fixed! Everyone here has dealt with Bar10 for the most part and can help you all the way.
I make custom parts also, so if you need something I could possibly be able to help. My pistons are good, and Springer makes and sells the S Trigger which is a Zero trigger and works with a 90 degree piston. I have an S Trigger on my M28 and a 90 degree piston and its pretty badass!
If your just starting airsoft, or even sniping. Gar rifles are not the way to go buddy. Upkeep and upgrades cost a lot! Spring rifles are easier to fix, and parts are much much easier to find.