IMO the difference between PSC and PSC+ is quite substantial - the later sounding much purer. But the REAL difference is going from AQ copper to AQ silver line of cables. KE-6, which costs almost the same as Volcano, is not even in another league - it is in another universe than the Volcano.
I went through AQ CV-4, Gibraltar, Volcano non dbs, KE-4 and now I own Kilimanjaro (one step above KE-6) and absolutely love it.
If you are on the budget, you may also try the KE-4 silver speaker cable, which is much cheaper than the Volcano. It still posses much of the virtues of the more expensive silver cables, at a cost of an absolute bass slam and extension (after all, those are 4 tiny silver wires).
I went through AQ CV-4, Gibraltar, Volcano non dbs, KE-4 and now I own Kilimanjaro (one step above KE-6) and absolutely love it.
If you are on the budget, you may also try the KE-4 silver speaker cable, which is much cheaper than the Volcano. It still posses much of the virtues of the more expensive silver cables, at a cost of an absolute bass slam and extension (after all, those are 4 tiny silver wires).