The 2013 Acura TSX remains a step smaller than the TL sedan, but you might be surprised to find that there's not all that much of a difference in interior comfort.
The front seats you get throughout the TSX lineup are impressive, as they fit a wide range of sizes and are quite adjustable; they do tend to be on the firm side, however. In back, the TSX definitely borders on tight on legroom for six-footers, with headroom limited as well, but four average-height adults can fit just fine--much better, it seems, than in rivals like the Audi A4.
There's plenty of space for cargo as well. The trunk in sedans is surprisingly roomy, and the Sport Wagon models have more space and a low flat floor that does come with one sacrifice: There's no spare tire on that model (just a repair kit).
Ride comfort can be a bit on the firm side, but it's about on par with other mid-size sporty luxury sedans; although some coarse road surfaces can transmit noise into the cabin, it's reasonably tight and quiet most of the time.