If you can find an old copy of the Audio Perfectionist Journal, Richard Hardesty does an excellent comparison between Theil and Vandersteen.
I think price wise, a better comparison would be between the Theil's and the Quatro's.
I owned 3a sigs for a long time. The Quatro is a better speaker top to bottom. The 3a Sig is an excellent speaker but with the built in subs of the Quatro, the integration is better.
Theil's are good speakers but you must pay close attention to what components you use with them. Vandersteen's are more forgiving although the Quatro gets bright with the wrong electronics.
I think price wise, a better comparison would be between the Theil's and the Quatro's.
I owned 3a sigs for a long time. The Quatro is a better speaker top to bottom. The 3a Sig is an excellent speaker but with the built in subs of the Quatro, the integration is better.
Theil's are good speakers but you must pay close attention to what components you use with them. Vandersteen's are more forgiving although the Quatro gets bright with the wrong electronics.

