Choosing a good preamp

Hi guys
recently i got my first peace of mcintosh MC275 limited edition but currently feeding it by the pre out stage of my Vincent integrated SV234. 
Experiecing the unbelievable difference and soft tissue of output, i am planning to buy a PreAmp (preferably Mac as well) on next move.
Any recommendation of which series of C xxxx products or even other brands which is match with mc275.
Is it better to go with tube on pre stage as well?
waiting for your kind advise 
kamiar