whats the best pre amp to pair with Bryston 4b cubed? A

The Arcam is a nice amp. I'm not convinced it's going to make a huge jump.

I tried a set of 7b3 monoblocks in my system at one point in time.  It turned out to be pretty good after an internal fuse upgrade, but the overall sound was thin in bass, midbass, midrange.  I would pair this with a very thick sounding preamp with heavy on the midrange texture and warm slow bass.

This is my experience also.I did not work together with audio research ref3 preamp

Thin and bright sound.Things improved with onkyo p3000r preamp

The cubed series seems to have thickened the house sound of the Bryston line to add more tone and heft to the sound versus earlier versions.  I will just say this — I bought a Bryston BP6 because it was supremely transparent and provided the most unvarnished and clear, 3D soundstage I’d ever heard in my system, by far.  If you’re looking for no coloration and an expansive 3D soundstage, go for a used BP26 and you’ll be thrilled.  If you’re looking for more flesh on the bones, go for a VAC or deHavilland kinda thing with tubes if you’re not opposed to that.  Just depends what sound characteristics you’re after.  But, if soundstage and transparency are your primary goals, get a BP26 and you’ll be thrilled. 

Have you looked or listened to other high end brands besides Bryston?

Firstly thanks to all for the responses.

For me the totems are keepers-not least because over and above their merits changing the speaker leads inevitably to considerations of electronics and synergy.

Ie I expect if I change the speakers other things as well will be gone,'

As it happens an electrician is coming in in March to cost out installing a new out let in the basement to accomodate a walk in freezer my wife wishes to buy-Im thinking might as well run a dedicated line at that time to the listening room and ugrade the service to 20 amps .

When that will be done dont know but agreeing on price in Mrach probably not till early summer.

So plan is get 20amp service including hospital grade outlets and see where we are.

Noting people arent convinced a Brtyston is markedly better than current arcama49  a vacuum tube preamp is on the list -I can put the arcam into bypass mode in that case.

If that yields results stop there if not consider another amp with Bryston up first

If that doesnt work change out the bryston for another amp or in the alternative try to audition a bryston cubed amp with a bp 26 as one of the posters suggested.

At any rate thats my current plan of attack (unless someone detectes a flaw in the reasoning)

Should be able to make a start in mid summer I think and will report on rrsults thereafter.

Again thanks to all responders