Dvlax, I would say that most AA members have a stock AEG. Those that have more than one usually have one that is stock for a backup, lower FPS powered games or just because they like the looks of it. You probably have heard this before but I will say it anyway - If you only have one AEG keep it stock, it is less likely to fail you in a game. Unless you are experienced at messing around with AEG gearboxes you might want to wait to upgrade for a bit.
I used my upgraded M4 for the first time this weekend at Crimson Dunes. I upgraded it with a full cylinder and a PDI 150 spring. It fired over 380 fps in my backyard but in Cali it fired an average of 370. Other than the BB traveling faster I can't say I noticed a huge difference in range. Even when I play with my stock SR16 I can't say I really feel all that <i>outranged</i> by anyone. The difference in range is not as huge as some think.
<img src="http://www.stopstart.fsnet.co.uk/smilie/shootout.gif" border=0> Its ok to love your AEG, just don't <i>love</i> your AEG.