this amp is a current monster; i'd even consider trying it in place of your thresholds, even tho the wattage rating may be less. i own a pair of the dual-mono iterations, the aw75dmb's, which can be run balanced, single-ended, or bridged. i used to use them wertically bi-amped on my main speakers to great effect. (for several years, i only ran one, until i found a second to match; even a single amp was superb - even on the difficult-to-drive thiel 3.5's.) now they are relegated to subwoofer duty, as i prefer tubes for main amplification duties. tho ec amps are certainly not dry, they don't have the soundstaging and warmth that good tube amps bring to the presentation.
re: preamps, i used to run an old ec-a1, which was also wery nice. i imagine the more modern 4.5 will acquit itself well. again, i ultimately prefer tubes, especially at the preamp position. but, ec is nice s/s gear...
doug s.