Budget M16s. Which has the best internals? What about ARMY R85??

Once again, I am finding myself looking for a new AEG. My wife got herself a CA36, with two mags, all for $120 shipped. Not bad.
Now I am looking for a good AEG. Ideally, it would be a CA SAR41 ES (G3A4), however, this being unavailable, I am considering another AEG. I already have an AK, the AK that I truly want (CM048SU LONG) is unavailable in USA, much like CYMA CM052 RPK which is also unavailable.
A) M16. Yes, I know, I know. KWA is Don\'t use the Lord\'s name in vain. of all it surveys. Now, if someone would give me $315, I would buy it. But I am operating on no more then $200 budget. After debacle with G&G $355 M14 veteran, I will NEVER buy another G&G product, so please, do not suggest it. In this budget there are following AEGs:
1. AGM M16 A4
2. A&K M16 A4 SPR
3. A&K L300 LONG
4. JG M16A3 Enchanced
5. DBOY M16A4
What I am looking for is sturdy externals (metal or plastic, don't matter much) and upgradable INTERNALS (which means MOTOR, Gearbox and Gears). Which one of these is the best? No matter what I get, they are getting a madbull tightbore:-)

B) My other choice is ARMY R85. I have a weakness for bullpups, besides, R85 looks a lot like Russian OTs-14 Groza. I know that the R85 gearbox itself is a beast. What about motor/Gears. What parts do I need to repair/upgrade it? Is it worth getting? What piston/piston head, cylinder/cyllinder head does it use? What gears? I heard everything is pretty much mix and match.
Any data on it?

Thank you

I'd stay away form anything of those, all of them have quality issues from what i've heard.

The ARMY L85A1 is a great gun from my experience with it, i really loved mine. The only issue i had with it was the fire selector slipping due to the vibration of the gun firing causing it either stop firing or slip into semi. Another small issue is that it's practically useless in semi. Due to the GB design i've heard you must fully pull and release the trigger in order for it to cycle. If you don't you need to switch to full-auto and and fire off a burst before using semi again.

Oh and the R85 is almost an exact clone of G&G's version by the way.

I know it is over your budget but you should get a G&P M4 SOPMOD. They are awesome guns and SnoSnipe can attest its quality.

If you can handle mildly wobbly barrels, you could get an Echo 1 "STAG-15 VN" M16A1

To be honest, I would recommend the ASGI G4 Series. I'd take a peek at some of those. They really are so versitile and so well made that you really just can't go wrong.