None.
For me, Trace gear is solid rehearsal room gear, and almost universally loved only by slightly older blokes who remember when the brand was breaking new ground in the '80s and '90s. I've played through way too many Trace combos and heads with those annoying 'all or nothing' EQ push switches, the graphic EQ that doesn't really help (the 80 hz thing does nothing on a 115 combo that can't reproduce the fundamental of anything below the A string), and they all seem just a tad short on power when you want them to really deliver the goods. Nothing like having the port chuffing away when you try and keep up with a 30 watt Vox guitar combo.
The differences seem to be whether it is the combo with the scary UV light on the front, or the built in compressor... they all look fairly heinous and dated.
Like Ashdown, I've never played through a Trace amp I've genuinely liked. Like Ashdown they all seem to be loud, slightly unmusical Vanilla. Like Ashdown I seem to encounter bassists who think they are getting a nice warm, grinding and organic tone from their Trace gear, when in fact they are getting a clean, un-nuanced honk instead that they've simply grown massively too comfortable with.
To start off, your post in a thread like this doesn't make much sense to me.
The OP is asking for suggestions to help him bring back more of the old Trace Elliot tone, and I assume your mission despite all the negative crap you write after all is not to obtain the complete eradication of an amp and tone a lot of people who don't agree with your
opinion actually love.
Not everyone has the same taste, as you might have discovered from own experience, just look at peoples taste in music.
Just because it differs from yours doesn't mean it is wrong.
That's the kind of mindset that starts wars, literally.
To comment on your subjective opinions from my view of things:
As the other guy who commented on your post I can start off where we agree, I too find the pre shape buttons on the Trace amps completely useless.
I love me some mids in my tone, thank you.
What's beyond that detail though I absolutely love.
Yes, I would be old enough to remember and have played in a band in the mid 90's where the Trace Elliot brand still existed independently, however that is not why I love their amps.
It wasn't until around 2010 that I discovered how great they sound and work for me, when I borrowed a GP12 Series 6 amp when rehearsing with my band, that they happened to have at their rehearsal space.
Since I bought my own GP7 SM amp, and it sounds just as great as the Series 6 did.
Best tone I ever had, and I used to play an Ampeg B-15S, which is also a great amp, just happen to prefer what the Trace does to my tone.
Yes, it does color my tone quite a bit, but to me that is an extremely desirable color.
I have no interest in a sterile Hi-Fi tone.
I still find the Trace tone to be a very articulate though.
Finally most people don't think about the the combos with the UV light on the front when they think Trace Elliot, those came after the iconic amps that people remember and love.
Haven't played one of those my self though, so can't comment on their tone, but I am of the same opinion as you, it does look kind of cheap.
Love the slightly more subtle red, green and black color scheme of the older amps though.