My friend used Ultra i/c and now upgrades to Reference MM2 i/c for preamp --> power amp. He said the soundstage and bass improve a lot. However, Transparent cables' treble is not as sharp and clean as those cables made of silver.
I have not used Transparent cables because cannot afford the price. But I should consider borrowing to try try
It's quite a big difference. However, the newer model doesn't mean it sounds better. It all depends on your system. I used both XL and MM1 version before but XL sounds better on my system. MM2 is too expensive and doesn't come up often on the 2nd hand market. XL or MM1 is good to start with.