I can tell you from personal experience, going from Quasi- to Full-complimentary was ear-opening. The tight, punchy bass, incredible headroom and lack of distortion - even at watt levels higher than what my speakers are rated for (and no blown fuses!) are leaps above my original 400-II.
A good friend who has been on a quest to buy the best damn tube amp he can find has been auditioning systems for the past several months. While he had been convinced the tube amps sounded better than his stock 400-II, even some legacy McIntosh amps, he wrestled with the money commitment these sellers were asking. I finally convinced him to come listen to my system ... nothing esoteric - a Topping D50s, upgraded (not BillD) Carver C1, and my WOPL'ed 400-II driving a pair of a/d/s/ L1230 (as well as a pair of L1290 that I use to go back and forth).
He was immediately sold and gave me the down-payment to buy the WOPL Works: PS caps, Control Board, Backplane kit, transistors for full-complimentary, and rectifier snubber board - as well as Don's Watt's Abundant speaker protection board. His amp was 100% stock and fully functional but he loved the warmth and tight - QUIET - system he heard at my house.
You too will be very impressed ... the old, even re-capped, PS equipment is decades dated - and in serious need of upgrading.
Not sure if you are aware of the comparison of Full- and Quasi complimentary, so I grabbed a screen from Joe / Gepetto / Mr. White Oak Audio where he explained all ... to save him some keystrokes.
Enjoy!
Al