more ground clearance? Thats a tough order, as it is usually the headers that present a problem, not the sub. Only real way to fix the header issue is to either get different headers, or raise the engine (don't really want to do that as it would raise the center of gravity).
Another options is 1/2 height body mounts, but this can create problems with some transmissions.
As far as better ride-this can be interpretted many ways: Street ride, track/street track only, etc.
Many people with more knowledge than me would say that you can spend 1/2 as much $$ on upgrades to the stock sub and get the same or better benefit in handling than an aftermarket.