PS Audio BHK lacking..

Something definitely sounds off with that particular unit's performance, and I suppose it could just be worn out tubes or poor tube choice.  I ran one for ~3 years with much satisfaction.  It replaced a VAC Ren Sig II convincingly in my system, and I only moved on for an AR Ref 40, which does offer more, but doesn't exactly embarrass the BHK pre.  I found soundstage depth and bass to be strengths of the preamp, not weaknesses.

Trying a new set of tubes is a good place to start.  Check out the PS Audio website forum for some detailed discussion threads about the many varieties that are possible, with a nice number of sonic impressions reported.  After comparing 10 different varieties, I was smitten with Amperex 7308's in the unit, because it offered the right balance of fullness in mid-bass through low mids that my system needs, while not sacrificing the highs.

Since you have a used unit, I'm assuming it is well broken in.  Several have reported some big changes in their first 100 hours (wasn't a big event for me when I broke in a new one).

I have tubes ordered from PS but I've read on here that others are better & I can't remember their name.

If the sound doesn't change for the better you should call PS Audio and see how they suggest you proceed.

Tunsgrams are the way to go though anything is better than the stock PS Vanes. Upscale audio has the specific Tunsgrams and it is a different tube type so you have to change a jumper on the amp when you swap the tubes. 

I had serious buyers remorse until I rolled in different tubes.  With the better tubes, it is a very nice unit.   

As tubes age they at the 'end of their lives' sound pretty lackluster.The gold lion tubes that PS Audio recommends are fine tubes but emphasize the mids and bass.A faster sounding lively tube is the JAN Phillips 12AU7.It's one to put on your list to try.