Do you want this for CQB & mid-range shooting, longer range shooting, what are your parameters?
Generally speaking the shooter and inherent accuracy of the rifle & ammo used are much more important than the optic or magnification.
For example, I could consistently hit the 300m gong (18") all day w/my 5.45 SAR-2 using cheap Wolf ammo & Kobra sight.
With my STG-556, cheap Silver Bear ammo & a 2moa Aimpoint I can do the same thing.
I find magnified optics more helpful in ID'ing a target than actually hitting it.
I've tried a magnifier/Aimpoint combo and didn't care for the magnifier (too much weight & effort for too little benefit).
If you absolutely must have magnfication then something like the 1-4x Millett DMS-1 isn't bad or you could cough up the big bucks and go for a Meopta or Shortdot.
If you're dead-set on a magnfier then I've heard some of the cheap knock-offs are better than others (supposedly UAG makes a better copy) but you might want to check out the LaRue Po Boy Special that will give you their excellent swing-aside mount & the surprisingly good Heinstoldt 2.5x magnifier for only $195:
http://stores.homestead.com/Larueta...ategory=Optic+and+Mount+Combos:Po+Boy+Special . If you decide to get an authentic Aimpoint or Eotech Magnifier then you already have the mount. If not you can sell it and recoup most of your money.
Aimpoint vs Eotech has a lot of personal preference involved. While I prefer the Eotech's reticle it also has much less battery life & more reported problems than the Aimpoint. If possible, look through or try them both.
HTH...
Tomac
ETA: A decent magnifier should work w/any decent red dot sight provided they're at the same height to line up properly.