What speakers for $5K Used?

Your dealer may not carry the 10T's any longer. After 10 years of mfg'ing the 10T's, Aerial just stopped making the them in the last few months. The new flagship for Aerial is now the Model 20T. The 20T is about $20k retail.

You may want to try a new pair of Magnepan 3.6s. The large, immediate and dynamic soundstage very well may give you a new lease on life. The Maggies have their drawbacks but, the large and immediate soundstage, and truth of timbre are not among them.

One of the greatest things about this hobby is that we can change around and try many perspectives in pursuit of audio nirvana. If you have not had dipoles in the past then I would highly recommend them. There are a lot of good ones out there.

Dynaudio Confidence 5, bar none. Standard setting details and speed, midrange to die for. Survey the C5 owners, they will all agree.

Check out Merlin VSM-M's

Merlin VSM-Ms, as mentioned above. Very good recommendation and a good fit for the Plinius gear you have. Would be "overkill" for home theater but won't need to upgrade for a long long time.