The general consensus is that AEPs are dogshit and a waste of money, poor performance and horrendous trigger response.
Better off with a CO2 pistol, work all year round, largely unaffected by cooldown, etc. This was recommended to me by @Colin Allen and he was absolutely spot on, and i've only used CO2 pistols since.
I have Umarex/VFC Glock CO2 mags i run in my other Glock GBBs without issue. Going by the SSE18 i'm guessing you're fine with Glocks, so worth a look. (I put the CO2 mags in my 18c and the full-auto is fast.)
Also have an Umarex/KWC CO2 H&K USP, which is really nice but all proprietry inside which mostly rules out upgrades.