Markfina,
How much do you want spend? I think if you want to stay with a moderately priced amp, a new Cambridge Audio Azur 651A or a NAD C356BEE would sound really nice with your Heresy's.
On the cheap used side, many 80's and 90's Denon integrated amps sound really good with Heresy's as well as fortes and Quartet's. I am currently using a Denon PMA-757(80w/ch) with my Heresy's and a 90's Onkyo Integra A9711(80w/ch) with my Heresy II's. Very punchy midbass and pretty dead on neutral.
Bill