Subwoofer with Thiel 2.4s?

Some of these details are in a couple amp threads that I initiated as I worked to build this system, but my real issue is that I am currently driving the 2.4s with a Pass Labs INT-30A. This combination, while sounding drop dead gorgeous with the right material falls flat on some more complicated stuff (e.g., rap, dance, & movies). I've tried another higher power amplifier (a 400 W Mac 402). This amp sounds great and solved the bass problem, but doesn't image quite as well as the Pass (or reveal as many recording details). I'm also considering a Pass X-250.5, but am still concerned that I'm going to end up missing what the XA amp gives me. It's just so good at imaging (which is the most important sound quality for me) and sounds so natural and grain free that I really don't want to lose it. I know the sub route is a cheating solution, but I'm on a budget and was just hoping that a little augmentation may let me fill in the low end without losing all of the positive qualities of the Pass XA series.

Thanks for the thoughts.

There was an SS1 on here that just sold for $900. I was a day late on getting it. Really kicking myself over that one, but I had to finish my taxes to know what the money situation was going to be. Damn.

Well, I picked up a REL Storm III. My plan was to use it as a high quality "hold-over" until another appropriately priced Thiel USS/SS1 comes up. I'll comment on the sound when I get the REL in later this week... and will update the thread if I end up comparing it to a Thiel Smart Sub.

Hopefully adding those final low frequencies to the Thiel 2.4/ Pass INT-30A combination will allow me to focus on buying new music...

I have to say that I'm extremely impressed with what this sub did to my system. Like others have commented, adding the sub opens up the soundstage and adds depth to pretty much all the music I listen to. I also watched Salt and listened to Tupac's All Eyes on Me, and the sub really made up for the previous bass deficiencies that had made these types of material feel flat and lifeless before the sub. Yesterday was really the first time I've been fully satisfied with the stereo since beginning the upgrades in December. I may eventually upgrade to a Thiel sub just because of the Thiel main speakers, but honestly, the REl does integrate very well. Sounds great.