I have heard the Matrix series driven by a Quad II at 15W,but I believe that they do like the power.You might wait and look at 100W+.After having a discussion with Kent @Pass Labs,I have come to understand that there is no jump between the .5 and .8 amplifiers (completely different circuitry.
My advice would be to hold out for more money and power.Contact Reno HiFi,as they have a 15 day audition period.You will still be responsible for shipping,but the expense is significantly less.