WBT Topline or Nextgen RCAs for Pass X250

Any joy you might gain by a 1/2% improvement (doubtful) would be negated by the recovery from surgery to repair the slipped disc you'd get from moving this amp to the workbench. Any time you move a component, especially a heavy power amp, you risk a scratch, bent heat sink or worse. As we say in the south: "If it ain't broke, don't fix it". Sit back and enjoy the music.

Agree with Elgordo. Big amps are not light.

Hmmmm...one wonders if the NextGens have actually been listened to, or if this is similar to the "reports-of-my-death-have-been-greatly-exaggerated."

I installed NextGens, and while I cannot speak for the toplines (never heard 'em, so it wouldn't be ethical to comment on 'em), the NextGens, as posted recently, are wildly good. And wildly means,you do not have to strain. You just flip the preamp out of mute and allow gravity to draw your mouth wide open down to the floor. If you really want to make it fun, listen to the RCA 0110 NextGens after 48 hours and plan your immediate ascent into Valhalla (and I don't mean Nordost!).
I know nothing about alloys: but I hear opera nearly every week, as well as the piano in my boyfriend's living room, as well as his friends, who sometimes sing at the Met. I hear voices all the time -- and not in my head. And I tell you, the RCA NextGens are the Next Big Thing.
My momma told me, if you never ate squash, don't say you don't like it: it makes you look stupid. I try to only talk about things I've experienced. I've experienced the NextGens, and unless you have a far superior RCA plug (if there are any, and I'll allow for that!), you cannot possibly NOT hear how the human voice improves: you can hear the "mask" of the singer as seldom before.
Common sense should tell you that installing Next Gens sure beats spending $1000 on a new CD player, or $5000 on new speakers.