My 2 pence worth...
There is a dude on the classified board selling a 4x4 shocker set up for £180, including bottle, barrels, hopper etc. I have been playing 8 / 9 years and played with a 4x4 for at least four of those. Its a good, reliable, accurate marker that can be set up in a variety of ways and will cause you very few headaches. I know from experience that it can be set up to fire fast enough to keep up with top end markers (but it wont be in the same speed class as them, to be honest) but it wont chop paint while it does it.
People will post replies saying "Its a big, fat B*stard of a Gun" and it is chunky, but you could do much worse. I seriously considered picking it up as a spare.
Whatever you do, best of luck dude. Second hand is the way forward, paintball is expensive enough as it is.