MC transformers - what do they sound like?

the transformers sounded a little more dynamics in the bass

I think you'll find this is due to better loading -- rather than a characteristic of trannies at large.
What a well implemented tranny should offer is a little bit of extra signal purity...
Makris explains all of this above.
You can also consult Stevens & Billington's (S&B)site (link above, FLemke) for some implementation info.
Finally, experience I've with S&B trannies is very encouraging. I believe Bent uses these for their products.

Gregadd sez

Transformers make it easier to magnify the signal

These trannies increase voltage at the expense of current -- they can't increase the energy, as you doubtless know.

Downunder: if you're interested in improving your EAR, check a relevant thread by Thorsten Loesch (an advanced diyer)[url+http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=2052]here[/url].
As to the note by the TNT writer, he's referring to *circuits* (and many circuits fit that description); components used in a circuit have this bad habit of drifting with temp (& voltage for that matter).

If what Raul is to make sense, he is using a very well stabilised active circuit and he's using his components in their optimum operating region. That's difficult and painstaking to design and implement -- but better (even in theory) than using a tranny. But let's face it: as Gregadd seems to imply, a good tranny, while expensive, is nowhere near the cost and rarerity of an outstanding fully active 80-100db riaa.