As a conference, the A-10 consistently ranks at the bottom of the "big 6" (Big East/ SEC/ Pac-10/ ACC/ Big 10/ Big 12). That's no turd of a conference. The top teams can hang with the Big East's NIT-level teams easily, and at their best could probably compete with the last couple of entries in the NCAA Tourney from the Big East on a regular basis.
I'm saying: Xavier can hang with the big dogs.
Yes Sean Miller and the great coaches Xavier has had before him have built a strong program at Xavier. Have no doubt they'll be pretty good but beyond that your A-10 points are off the mark. They are not year to year a dominating mid major conference, unless we've jumped into a time machine. They are in the mix with a glut of strong mid major conferences on a year to year basis, from CUSA to MVC to Mountain West, WAC and WCC. You're vastly overrating the A10 to say that they challenge the BCS conferences more than they try and stay in step with other top mid majors.
I think - and note I am specifically talking about the tops of the conferences - that the A-10 is as good if not better than those conferences. But it ebbs and flows; sometimes, like other mid major conferences, they only get 1-2 teams in. But Xavier's been a tourney mainstay for like 15 years; St. Joe's is always close; Temple's been knocking at the door; Rhode Island and Charlotte have their years.
Certainly, the Mountain West is stronger right now, and the Missouri Valley is coming back (they only got one team in last year, I believe). But Conference USA has Memphis that can hang with the more mediocre Big 6" teams and the WCC has Gonzaga and a budding St. Mary's. It's not a vast overrating of the A-10 - they're not the Southland conference or anything.
I guess I'll edit what was said before to be more accurate. I'd rank the A-10 along with the Mountain West (which is better and deeper) and the WAC (also deeper). Conference USA has Memphis rising their tides - the other teams aren't unlucky, they're also not that great. The Missouri Valley has some depth but their top teams haven't made a strong out of conference showing recently.
And in all of this talk about mid-major strength, I'm giving subjective answers. Teams like Temple, St. Joe's, Creighton, Utah, Southern Illinois often find it hard to build a schedule of mid-pack Big Conference foes that definitively show that they're as good as the St. John's and Penn States and Auburns of the NCAA. So I don't know.
But I think the A-10 is consistently good.