Morrow SP7 Upgrade.

Currently using Morrow SP4 Speaker Cables on Low Frequency (bass) in bi-amped system. Various Speakers used, at the moment Revel Ultima Studio. The Morrow's sound best of the cables I have driving low frequencies. At the moment Morrow have 60% off in their trade up program, (I would trade up SP2's I have in a budget system). Anyone have experience going from SP4 to SP7's, and how much better? What other alternatives for bass frequencies would you suggest if not the SP7's?