the stock I bought was:
14.99 plus 5.75 shipping
it's a good stock... the only thing I had to buy was a butt stock pad... it adds an inch of cushioning and it's made of rubber... I hated the plastic bumps on the stock... kept digging into me.
The barrel I bought for mine are a 12" Lapco Bigshot barrel with a .687 bore and now I have a 14" Lapco Bigshot barrel with a .689 bore. The 12 inch barrel with Diablo Heats and compressed air and I was shooting on average 280 fps. With the 14" barrel I was shooting 276 fps... I'm assuming that I lost some fps due to the slightly larger bore. Both barrels I bought were around $50 each.
So far these are the barrels I found that would fit the MR4 shroud other than my crappy RAP4 rifled barrel... I tried my JJ ceramic S2 barrel but it wouldn't fit into the shroud. The part after it screws into the gun was a tad too wide. I barrel outer diameter should be around 7/8" I believe.
As far as the E-trigger... I put one on my MR4 and it works great. Fitment was perfect... altho I don't know if there's any difference between that and the imagine e trigger.
If you want to get a front hand grip try this place... they have a nice selection...