Tube rolling suggestions for Unison Unico

My experience with Siemens E188CC is that the bass is not as strong as with Siemens E88CC, however they are anything but slow, and the image they produce is sensational. Slow is an adjective I'd never ascribe to Siemens tubes. Frankly, something seems off with your tubes if this is what you are hearing.

The Mullards are slightly, and I emphasize slightly, softer in the upper mids and highs than the Siemens, but they are not more laid back in the mids. In fact, the Mullards have more pronounced mids than Siemens or Phillips tubes, IMO. If Siemens are Eva Langoria, then Mullards are Eva Mendez. A little rounder, but equally as sexy.

Don't overlook the Raytheon and RCA tubes simply because there is little buzz on Audiogon about them. They are both excellent tubes, and screaming values. They can certainly hold their own with Amperex, Phillips, Mullard and Siemens.

Well, warming up overnight sounds appropriate, I think Tvad may have a point-maybe something is off with these particular tubes... although I would be hard to believe given that they are tested and all from Uscale Audio. But I think what you are looking for is probably the Mullards... given the description above...
Keep us posted on how this goes...
Good Luck

i use mullard cv4003s in my unico cd and tung sol blackglass in the unico amp. deep base and excelent mid, great for jazz.

i have noticed that many of the current tube designed preamps and cd players are not very tube sensitive.

i can't say the same for amplifiers.

older products are more tube sensitive.

In my unico I've tried several different tubes. In my system, my experiences are:
Radiotechnique: Beautiful airy treble - no bass at all
Mullards: Too Dark and syrupy for my 'modern' taste in music.. fantastic with pre-1970s music recorded on valve equipment though (loves my bossa nova collection!!)
Brimar 13D5: Better balanced than the Mullards I had..still the same house sound, but less so.. lots of missbass punch, high treble could use a bit more refinement
Siemens E88CC: Beautifully liquid, cyrstal clear, well balanced..perfect -EXCEPT they lack dynamics!!!
Amperex/Beckman 7316 Holland: So far, the best I've found.. Slightly drier than the siemens, but WAY more dynamic.. HUGE, precise soundstage (best of the lot), well balanced (perhaps just slightly tilted toward upper/mid, lower treble..but in a good way!).. not cheap though, but worth it!!