Should I sell my Thorens?

I have just completely rebuilt my system & moved it into my office. I have been downsizing so I figured I could let my VPI HW19 MKII with a Premier arm & modded Grado cart go. Well I ended up with a Thorens 160 with the original arm & Grado blue cart, that is supposedly set up by a pro. Upon listening for the first night I was horrified to hear it. The turntable sounds fine on simple passages but once it get's busy the sound starts to dissenegrate. I was listening to The Grateful Dead Europe '72 album & as soon as the band starts to pick up the pace the music becomes blurred, to the point of white noise/static. I cleaned the disc & listened again hoping the sound would improve but it did not. So I swapped out discs & found the same exact thing on another album, great when it is a vocal & guitar but static when the rest of the band kicks in. It was so bad I switched over to CD.

So my question is, even if I pay someone else to set the deck up & possibly even tweak it will it ever compete with what I had? I could also sell it & buy any number of decks in the under $700.00 range such as the Rega's, will they be better dollar for dollar? As you can tell I listen to rock music, I prefer all the seventies clasic rock bands & obviously the pressings are what the pressings are from that era.

My new system consists of B&W CDM1 SE monitors, Zu Cables Wax shotguns, McIntosh 6450, Monster HTS 3500 power center, DH Labs interconnects, Onkyo SP100 universal player, Cambridge Audio 640p phono pre & the Thorens 160
ditch the old grado blue....a weak link, and it may be defective.
Ditto "Jaybo", also check your stylus pressure.
None of the decks you mention come close to the HW19. Forget the Thorens and Rega and get another HW.
The problem could very well be your cartridge. I have a Grado Platinum on my TD160 and it is a great combination - beat the pants off of my Music Hall MMF5 after I made some of the tweaks recommended and described in detail on the following link:

Seems there's quite a cult following on TD160s and if you do decide to sell there should be a good market for it. But I'd strongly suggest some of the tweaks and a new cartridge before you decide.
I see the cult following but I wonder how easy it is to beat the performance of the Thorens with a newer deck, doesn't seem to be any easy answers.
a new thorens(td350) or a comparable new table is going to take you well over 3k....a vpi boyscout is pretty good for 2k, but a good cartridge on a td160 is still comparable.
I had an older Thorens TD-125 II in the late 70's w/ a Grace 707 tonearm and GAS Sleeping Beauty cartridge. It sounded fine until I began working for a high end dealer part time while going to college and upgraded to a Linn Sondek LP-12 and there was no comparison. The Linn smoked the Thorens.
I agree on changing the cart, an AT440ml for $90 would be a noticeable improvement. You should also consider having a better arm mounted on your 160. Linn??? You can also have LP-12 springs installed. Lots of things you can do to improve your Thorens. Do you question the setup done by a supposed pro?
I agree about checking the cartridge weight. It sounds like it is too light and mistracking on heavily modulated grooves.
I do question the set up, the cart doesn't look aligned to me with my simple turntable basics aligner. I thought about upgrading the cart, the arm & having it set up so at least I have a starting point but with all the added money wouldn't I just be better with a different table? That is the question I really need answered, should I sink $300-400 into this table or sell it & put it towards a different table?
I'm no fan of older lower-end Thorens' (compared to a VPI) but the problems you describe sound more like arm/cartridge issues. A 160, properly set up with a decent cartridge, won't have the issues that you're describing. If it was a used cart. and assuming it really WAS set up by a "pro" it may be the stylus is just worn out.
I have cleaned the stylus, set the stylus force & aligned the cartridge. The table does sound better but still not what I want. The cart was so off I can not imagine a "pro" did anything to this table.

Futzing with an unsatisfactory turntable shouldn't cause consternation, stress or brain cell death.