i was having this same delema about a year ago. I absolutley could not decide what to get, i started looking at both guns prices used. I found that you can get a very nice mag for 250$ or less. Leaving you with plenty of money to buy a good air system.
As stated before you can have a the most rockin mag for about 400$ in upgrades if you get these things; lvl 10 85$, retro valve 200$ (trade in program) and a intelliframe 115$.
Another option that will be out soon is the medusa frame, noone knows everything about it as of now but it's suposed to be using magnets, possibley electronics and is suposed to be very sweet.
I encourage you to look on clasifieds forum here and you can find great deal from very trustworthy people.
Minimag body, valve: CF05240, gas-thru grip, all-american, lvl 10, tourney velocity adj., flatline 68/3000 nitro FL01255
custom spyder, with every part replaced but they valve and body.