I think that the Sigtech is significantly better and significantly more expensive. You can reach Sigtech at (617) 995-3500. Tact vs Sigtech has been discussed rather extensively over the last year. Check out the following threads:
Is TACT RCS 2.0 truly transparent
5 followups, last on 05-15-01
TACT RCS 2.0 Users Group
19 followups, last on 04-10-01
Tuning speaker / room response?
20 followups, last on 03-21-01
carl's area
14 followups, last on 04-21-00
TacT Room Correction System processors
7 followups, last on 09-17-00
Room Correction Systems?
10 followups, last on 11-14-00