At the end of the day, most mainstream amps are coloured with a mid scoop to make jazz basses sound good in different ways. Mark Bass, Peavey, SWR, Ashdown and most of the hybrid heads for example.
Since I don't own a jazz bass, and my Smiths already have a mid scoop in the voicing of the instrument, many coloured amps make my Smiths sound like there's either a pillow over the cab or remove the mids altogether. Given one of the Smiths is fretless, I need the mids to pitch myself.
Trace stuff has been ok for the mids but they're a very aggressive amp with a scoop towards the lower end so I get lots of boomy thunder and some bark but the mids are reduced. I have to use pretty extreme settings on the graphic.
The only reasonably priced amp manufacturer I've tried which isn't prejudiced against the colouring of my Smiths are Gallien Krueger. I get lots of mids, the RB700 combos I use are clear enough that they sound as good as a PA with CD's through them and there's oodles of club filling warmth and punch if I need it. The only time I need to tweak the eq is when there's some onstage acoustic issues (like too much boom).
I can play any of my other basses through the combos as well, and they all sound the way I need them to for me to be able to hear myself clearly on stage. If I need extra volume I can whack a 210Rbh on top of the combo and have enough volume for any venue up to a thousand seater.
But back OT. The amps that have impressed me the least were the Fender solid state BXR range and Marshall's solid state stuff. Both well established brands that seemed to be trading more off their guitar heritage than trying hard to deliver quality bass amplification. Both sounded very coarse and boomy, the features on the amps were limited and overall I was just left thinking 'why bother'?
I suppose in Fender's case, because they own SWR now they don't have to work hard to market bass amps under their own brand. Speaking of SWR, I had problems with volume as well when I owned an SWR Bass350 and a Triad cab.
The Triad cab was only rated 98dB sensitivity and I suspect this along with the 8ohm impedance would have been the cause of the lack of volume in my case. I was probably only getting 250w or so.
For Peavey stuff, I used to own a 410TX cab which seemed to have a lot of clack and boom but no mids - I wondered if this might have been a phasing problem but I sold it before I could find out. The Peavey heads I've tried (Mark VI, Mark IV) deliver what's needed to be heard on stage but not much more. I had a TNT150 combo once as well which was pretty good but compared to my GK combos, it didn't do mids very well either. I've also tried a 450w Databass combo and that thing was very impressive. I wish they'd bring it back with neo speakers - it would be a fantastic package.