So reporting back after a month or so after installation.

The cheapo motor mounts work just fine! It's dead quiet at freeway speed. Sometimes I can feel a bit of vibration through the pedals at idle, but not bad. I get in my GF's Honda Civic and it makes me really appreciate the quiet smooth ride (and sporty, but not harsh, and not mushy) ride of the B7. Then again, I racked up 50k miles in the year and a half I've been with her. I tend to be the one driving on weekend road trips. Her '97 civic has 80k miles on it. We need to even things out.

But, I still have the mysterious clunk in the front end of my car. I replaced most of my control arms and tie rod ends, and nothing feels loose... so, I'm at a loss as to what it could possibly be. I guess I just need to put a wrench on every bolt in the front end.