Rickysnit, I've done this, both the power inlet, fuse holder and internal wire to transformer, and the speaker wire from amp board to binding posts (along with upgrading binding posts), in a Perreaux PMF3150. Also replaced the RCA inlets with KLE Pure Harmony with VH Audio 21awg silver occ wire. All done in stages with testing in between.
For the speaker wire, the best improvement was eliminating the binding posts. I ran the same wire (VH Audio ofc) from amp board to binding post (which I replaced with WBT), then same wire from amp binding post to speaker binding post. Wiring direct from the amp board to speaker binding post was a definite improvement, even after the WBT change.
I have CSS speakers, and recently purchased the new tweeter and upgrade crossover - I soldered VH Audio 18awg UP-OCC to crossover, drilled 2 small holes in speaker and ran wires direct to the amp board (no posts in signal path), unquestionable improvement in what I perceive as 'speed' and 'resolution'. The same wire is used internally from xover to tweeter and mid. (Bass is handled by pair of GR Research open baffle subs).
I don't know about only changing the speaker wire internally, as I changed the binding posts at the same time, going from factory cheap steel to WBT (copper), with a small but welcome improvement. This exercise demonstrated just how bad it is having large chunks of standard quality metal in the signal path. You may find a slight improvement with changing just the wire, my experience is the binding posts are the biggest detriments, huge thanks to Ricevs on here for highlighting that which drove my curiosity and now much improved sound. For your Bryston, maybe try the wiring first, then try skipping the binding posts and wire either direct or as close to the amp board outputs as possible to see if there may be benefit.
