FYI, there's www.audioreview.com
for a general collective opinion on the two speakers you mentioned.
I personally owned the NHT 3.3, and I like it. Even though the base still goes low, it doesn't go low enough for HT (or even some music CDs for that matter). The NHT lines from 2.5i is 2.9 and 3.3. The 3.3 has better spaciousness compared to its younger siblings. Pairing NHTs with amplifiers is rather crucial on the treble side, harshness is usually exhibited on 'incompatible' pairings. Some people has mentioned cables make a difference with Cardas being one good NHT supporting cable being mentioned.
Haven't heard the Aerials, but in your price range, a LOT more speakers can be heard. www.unclestereo.com
has the 3.3 for $2900 (dunno about the service though, never ordered from them). One thing the NHT do well is they can play LOUD with low distortion. I mean like LOUD, LOUD, where you won't want to be in the same room as the speakers are.
Other speakers that I can recommend in the $4K price range is Magnepan 3.6 (require ample amplification - heard it with Aragon, and it was sweet) - very natural sound, but has a rather small sweet spot. PSB Stratus Gold-i, heard the Silver, couldn't find a dealer with the Gold-i nearby me, but the silver impresses me enough. The lows are not that of the NHT, but open speakers, and WAF is rather high. The Sony MM-S9 (Model # might be wrong) is another good one, but might be hard to find a dealer - lower bass than NHT, a bit short though, so standing up impairs the sound a bit.
Enough on my rant. Might be biased, but the thing I liked most about my NHT is that it can play LOUD and still sound clear. And that's about it http://www.avsforum.com/ubb/smile.gif