The only class of SCCA Solo II that doesn't let you play with the rear sway bar is Stock. And in Stock, you can't even change out the springs. So that's not an issue.

The Neuspeed bar doesn't mount to the firewall. It mounts to the upper A-arm bolts. Strut bars mount to the sheetmetal and indirectly allow less deflection of the upper suspension mounting. The Neuspeed isn't really a strut bar in the sense that it doesn't deal with the strut mounts. Regardless, it ties the upper A-arms together and prevents deflection, which is more usefule in a car with a double-wishbone suspension than to just stiffen up the sheetmetal around the shock mounts. Anyway, for any sort of tie bar to be illegal it has to be triangulated with the firewall, which the Neuspeed is not.

I like the Suspension Techniques rear sway/tie combo. Not as expensive as the Comptech setup but similarly effective. It "only" has a 19mm bar but generally people overlook the fact that thickness is not the only determining factor of swaybar efficacy. The geometry of the bar, mainly the length of the virtual lever arm which acts upon the LCA is a huge factor in how much torsional force the bar adds to the suspension. The ST bar is shaped differently from stock (and Comptech which is essentially an ITR bar with adjustable endlinks) and therefore is able to do more with a thinner bar.

Damn, if that wasn't wordy. Cliff's notes:

-Get the Neuspeed front bar, it's legal for STS and DSP if you're concerned with such things.
-Suspension Techniques rear sway/tie combo is dope and cheaper than the Comptech piece.