but you're the 2nd SB4000/SB5000 owner who has indicated "It ain't broke, don't try to fix it."
I think it's true in this case. East preamps are great, but so are the ones within SBs. If it was not, I would have J-Retro(ed) it long time ago. The Bromberg & SB preamps are by far the best Carvin ever produced. BTW, nice Roscoe on your avatar...I used to own one (SKB5 with slant pickups).
I myself can never leave anything alone!