Recommend a Used Solid State Preamp for About $5k

Well, I can recommend the Ayre K-1XE.
It is also very well reviewed, as is your ARC Ref. 2.
(I have heard both, as my friend has the same ARC. I agree that the ARC is a good preamp too.)
I will not say that one is better than the other, merely different.

The Ayre is very quiet with no tube rushing (obviously!) and a very low noise floor. (That is what I like most about it.)
It also has optional built-in phono boards that are very good. (Much better than the old ARC PH-3 which I used to have.)
It has a remote, although it is very basic, in as that it only controls volume and mute, unlike the ARC remote which will give you more controls. (Personally, I don't need more, as I typically only run one source, my turntable.)
It has a good number of inputs, 3 RCA and 3 XLR, and is a fully balanced design.

Personally, I am not sure you should change to a SS preamp unless you really can't stand tube rushing.
(FYI: Eventually the tube rushing got to me, and I made the switch to SS. And yeah, my hearing is sensitive to that particular noise. Most people can hear past it with no problem.)
If you can live with the tube rushing, I would not bother, as you have a very good preamp as is. (BTW, my friend has done some tube rolling to reduce the tube rushing and his is now much quieter than it used to be, in case this is why you are thinking of making the switch.) Plus it is my opinion that having some tubes in your system chain at some point is always a good idea. (I have mine in my Lamm M2.1 amps.)

If you insist on trying a SS preamp, the Ayre is a good choice. There are a couple of Ayre K-1s for sale here on Audiogon. (Unfortunately, neither is fully updated to the K-1XE model. I recommend spending the $1500 or so to upgrade it if you get one, as it does help a bit. Plus the E upgrade increases the gain of the phono section by another 10 db, (up to 70 db) which helped me with my low output MC cartridges.)

Good Luck!

Here's a SS passive pre that may challenge your Ref2: the Music First Passive Magnetic Preamplifie. If you do investigate this unit please be sure to report your findings; it sounds intriguing.

BTW it costs far less than your price but that does not mean it's not a contender; check out that review.

Nsgarch.....as you can see, I'm stedily creeping up the high end ladder....so yes I am going to get a pair of Pass X-600's to see how much they eclipse the four bi-amped Carver monoblocks in power, control and sonic purity.

If they don't eclipse the Carvers by a mile, I'll sell the Pass monos for what I paid for them. I can always use the Carvers for my home theater setup.

The best solid state preamp I've had was the Audio Research LS-10. When it was good..it was awesome. But on some recordings, it was missing a lot of information on music that I was very familiar with and that was very unsatisfying and it just annoyed the hell out of me to listen to a piece of music and it all wasn't there. Half of my recordings sounded awful on it.

I have $5k in my budget to try a used solid state pre to compare to the Ref 2. I'm not selling my Ref2 just yet. I want to compare it to a solid state unit in its price range to see if I like it.

The Ref2 has been excellent across the board, but I have never heard it compared to a solid state unit in its price range.....I just might like it better. Nor have I heard the Ref2 with amps higher up the food chain...like the Pass monos. Audiogon gives me the luxury to audition stuff and not get hurt too bad when I need to sell it if I decide not to keep it.

No offense taken about the Signal Cables, I know they can be improved upon. With a limited budget, my first priority has been with the preamp, now amps, then cables.

I'm never offended by the stuff I have....I go as far as my budget takes with me and I have to be content. But, I do keep meticulous notes of suggestions like yours, ...so when I get the dough and it's time to upgrade, I can refer to suggestions like yours when making my decision. So, thank you sir. I appreciate your comments and suggestions.

Well Mitch, with the Pass(s) and the Kappas and the ARC preamp, I'd say you'll have a very synergistic system. What I meant with my comments about the SS preamp, was that your ARC preamp is already a pretty elevated piece of equipment, so if you want to make a fair comparison, you'll have to spend some money on a SS preamp. More than $4-6K IMO. But frankly, I think you're going to love the tube/SS combo.

You might want to check out Edge Electronics they have a few good preamps. Another option is the McCormack line