What tube preamp to go with McIntosh MC275?


Hi,
I currently connect my DAC directly into my power amps.  Both my power amps has volume controls.  They are McIntosh MC275 and a customer built 300B.  Actully, I think they sound good, but I am wondering if it can be improved further by adding a preamp.  My speaker is Harbeth 40.1.  I don't need louder volume, so, I am purely looking for something to improve the sound.  If you ask me what I am looking for, I think bigger soundstage, more life-like, and more slam in the bass, I guess.

Any suggestions?  I can see many preamps use 6SN7 tubes, but my custom built 300B already have 4 6SN7s, I am not sure if it will make much difference by adding more 6SN7.  Would 45 make a good preamp tube?
gte357s
I am getting confused now. I borrow the A3300 from a friend and I don’t like the sound. It seems it filter out something. Music is not as engaging, and got fatigue after a while. I prefer to have my DAC directly goes into the amp, for both MC275 and the custom built 300B. It seems buying a preamp is trial and error?

or could it be the cable?  I only have two pairs of RCA.  One of them gives me that fatigue when I used it to connect my DAC and power amp.  
oldhvymec1.... So your telling the OP to get rid of his $15,000 speakers!? I think hes asking for advice on a Pre amp?

Not at all, I'm saying a 90% speaker with a 275 Mac and a C20 will have all the Umph you'll need.  I have a C2500, very close to the C22 (re)
BUT my C20, will just whip the pants off of the new stuff, just no remote.
MX110, MX120, MX121, C22 (early) 2 C20s, a C11, pair of C8s. I have a few pieces.
The C20 is the BOMB.. When it's right... FEW get even close. 60 years old. Cary, AR, VTL, I've had them all and still do have a few. That Mac, and something about the "Samra touch". (Red sock green sock guy)

Wonderful a Wonderful!!

Regards
Just an update, I found out the problem is one of the ICs.  I change it and the A3300 sounds very good with the 275.  I decided to go with it for now, and maybe upgrade later.