When I bought my SL3 back in 1996, I spent 1 year comparing it against the Aerius (not i), Apogee Slant 8 and Thiel 2.x. Comparing to the Aerius, the SL3 has a bigger, fuller picture of the band; the Aerius never gave me that feeling. Though, the SL3's picture might be a bit too big depending on room size. Perhaps sitting in the front vs in the back of a jazz club would fit the description. Dynamics feels better with more contrast.
After all these years, I truly love the SL3's precise imaging, air transparency and soundstage. Bass, however, leave me wanting much more especially when I listened to that B&W 801d in that store *by mistake*. For the price range, SL3 was THE BEST overall and that's why I bought it.
I would expect to get 1500 for my almost perfect condition SL3 when I buy that 801d... The only imperfection is that the panel slided down half an inch which I have yet to fix.
I would definitely upgrade to a perfect condition SL3 if I were you. Trading in your Aerius you are probably looking at $500.