Fairly certain it's not driver/sound card, might even just be me I've had my current speakers for such a long time I've probably grown accustom to them. Also I'll probably pickup a AE-5 in the not to distant future as I'll probably build a new PC.
Actually I just remembered something...I think I have actually experienced in the pass about what you meant about the "hollow sounding" that you describe.
Just get an idea, for your old 2.1 speaker set-up, you have the sub on the floor but the satellites speakers on the desk is that correct?
The thing about about T40 II is that its bass/low frequency would actually go all the way down to 35Hz, which means the bass would actually be comparable to , if not even lower than some 2.1 speakers; most studio speakers 4" inch bookshelf speakers will only go down to around as low as 70Hz Hz, which is good enough for music, but it's lack the rumbling sound effect for explosions in games and action movies etc.
The problem with the T40 II is that the low frequency and heavy bass if use on a bog standard desk with either MDF or chipboard, the sound will become distorted. A 2.1 speaker will not have this problem as the satellite speakers will only go down to as low as 120Hz, and anything below that will be pass onto the sub to handle (which is place on the floor rather than on the desk in most cases), and the highs and mids come out from lows essentially come out from separate units rather than altogether from a set of 2.0 speakers.
Believe or not, I have had the same issue even with my Monitor Audio BX2 on my desk, due to its bass/low frequency go down to quite low as well (down to 38Hz) and I was not getting the audio quality I was expecting with the sound (particularly the bass) sounded distorted rather than tightly controlled with precision. I gotten the IsoAcoustics ISO 130 Studio Monitor Stands and have my BX2 sitting on it on the desk, and it has minimised the distortion and sound very good now.
I actually gone from the T40 II, to the Edifier R1600T II Plus, and BX2 with the same distortion problem, before actually realising the problem lies with my desk, not the speakers. It's been a long time since I had this issue, so it was completely at the back of my mind.
Not saying your issue is definitely this as well, but it might worth to keep this in mind.