Vinyl sounds a bit thin and slightly strident.

Dgarretson provides good input on the TX2575 resistors. I just replaced 22 resistors in the audio section of a Counterpoint SA-2 with TX2575 and the clarity was greatly improved. I can relate to all the praise that Michael Elliot gave to these resistors when he compared them back in 2007. However they had little to do with the SA-2's incredible portrayal of space which is inherent in the SA-2's overall design. And I suspect such changes here will not be as beneficial as tube rolling (in the LS7) for the improvements in bringing more life to the mids.

Until you get those EH tubes out of the LS7, all the fiddling with cables is only going to result in one set of strengths/weaknesses for another.

I can not suggest a specific 6922 tube for the LS7 because one tube type might be so incredible in one product but be outperformed by another tube in another product. I have no experience with the LS7....only the LS5. And I did not go through the multitude of tube-rolling efforts with the LS5 like I have with other products since I owned the LS5. But the Amperex quite handily outperformed the stock ARC tubes in both the LS5 and the SP-10 that I had before it. There is so much to gain from the trials and patience of trying many tubes in each component.

The Tele 6DJ8 is the king in the SA-2 but in the Aria WV preamp, the Amperex 6922 works like no other. And in the CAT amps that I use, a number of Valvo, Philips and Amperex all work incredibly well; the Telefunken was not a good fit at all here with the result being a most flat presentation. Without trying these in each product, there is just no way to know.

From a view of the circuit board on the LS7, it looks like 2 of the tubes need to be the same but the other two you could try different brands. Maybe try an Amperex 7308 for a little more detail and dynamics and the Tele or Amperex 6922 for more midrange smoothness and bloom.

Once you get a set of tubes here that take the performance to the next level, the IC from the LS7 to your amp will be CRITICAL to achieve that next level of 3D performance.

The variety & multitude of suggested corrections & mods seems fairly overwhelming; who knows it could be any, or a combination, of the above.
One area I haven't seen addressed nor do you mention, is what AC cables you're using. Since the CDP is satisfactory, you might experiment with upgrade AC cord on the phonostage alone. Or line conditioning. Perhaps even footers or an isolation shelf. All of these can change sonic signature to a lesser/greater extent, especially with tube componentry.
Some here would argue that cabling & cords can't possibly affect the sound of a component. However my own tuning experiences with changing AC cords (and to a lesser extent, line conditioning) have proven that a world of difference can certainly be realized.
Just another mystery to throw into the mix - sorry ;-)

I have a question about effective arm mass and loading at the end but let me start by saying this.

Bob, I'm using stock cables on all my gear. The ARC stuff does not have user removable AC cables and I'm not planning on delving that far into tweaking by removing the stock cables at the moment. The only device I have concerning power is a Furman power strip that everything is plugged into. I am familiar with the benefits of using power devices having borrowed one to try on my system in the past and I'd like to own one in the future.

Jafox/Dgarretson, I like the valuable information you've written. I will have to keep your posts close so when I'm going to plunk down some cash for new tubes I have some sort of reference. Plus I'd like to give the resistors a try. Thanks!

The cartridge is 9.5g and it's looking for a medium to high mass arm according to Benz's spec sheet. However, I'm not particularly sure what the JMW 9 Sig. arm mass is. Also, I've figured out that other than light bass there is a response bump at around 3.5K that gives music a more tense feel. I'm sure it doesn't help that the most sensitive area of hearing lies right around that frequency. My question is will changing the loading resistance help this bump? I'm loading at around 2.5K/60pF(cable capacitance), the cartridge Z is 95ohms, Benz says load >1000ohm but I've heard about a 2.5/1 loading ratio which would put it @ 237.5. What should I expect if I drop loading to that even though Benz suggests 1K minimum?

N803, Bob is absolutely correct, the first thing I would change out is those stock power cords. I had a ARC SP 9 MK. III which had all the sonic limitations you speak of, putting in a IEC receptacle with a good power cord made a large sonic difference. I would absolutely make this the first change to make, all the benefits of other changes mentioned won't be realized until you take out that stock power cord!

Hire a local tech to add the IEC if you're not comfortable doing it, shouldn't cost much at all.

Actually there is a simple method to modify for testing upgrade cords without butchering the back panel, and at nominal cost. If you like the results then that can be done later... If not then you can easily go back to stock. I have previously posted this many times; here it is again:

Start by getting a male-prong IEC (which you may end up installing later - or not) there's many sources for this.
Cut the stock cord within about 6" of the component. Strip the ends and solder on your IEC. Use heat shrink sleeving, or at very least electrical tape, to insulate the bare connections.
Get a loaner upgrade cord from a local audio shop; these are usually used often so they're already broken in. After installation, leave the component energized for awhile (days) so it can settle in properly. Now you're ready to evaluate. Next, try out a different cord for comparison sake. No two cords sound the same on any given component, & what works well on any particular piece may not perform at all on a different piece so you need to experiment.

Some cords are all-purpose; others and intended for source-components only, which applies to most anything except a power amp or the input side of a high current AC line-conditioner.

If you want to return to stock cord, then just strip both the ends and solder-splice together again (or use butt-crimp connectors). Again use heat shrink sleeving for a professional appearance. You can heat the sleeving with the soldering iron, or a hot hair dryer, or even a butane lighter if you're careful.