Going SACD or analog?

Analog.

This is a tough call.

The first thing I would not do is abandon digital altogether. You have hundreds of CDs, no sense not being able to play those.

Your real problem is that you do not have a linestage or phono preamp now. These can be a bit pricy depending on the quality. If you had a linestage and phono preamp, the following advice would be different.

Frankly, here is what I would do:
Keep what you have and save your money for a nice preamp that has a phono stage in it. You might want to consider a used Krell preamp with phono built in. They are a good value, and will be good with the Plinius amp.

The next item on the list you need to get is some better IC's to connect your Preamp to your amp.

The next item you need to save for is a Turntable/Tonearm/Cartridge combination. Lots of good ones out there. Just set a budget and work within that budget.

My 2C.

KF

First, stop trying to confuse yourself. This isn't a technology choice. It's a software choice. Where is the music you want to listen to? Vinyl? SACD? No, it's in CDs. A vinyl rig won't play that, and a SACD player won't play it any better than a CD player will (in general). Do you want a vinyl rig? Are you looking forward to spending your weekends at flea markets and garage sales scouring bins for old records? If yes, then definitely go for the vinyl--it's a lot of fun, and there's a helluva lot more LPs out there than there are SACDs. (There may be more LPs out there than there will ever be SACDs.) If not, then maybe you'll have more fun playing with a new technology. But I'll bet you that no matter which way you go, five years from now you'll still have more CDs than anything else.

I was in pretty much the same place as you so I'll tell you what I did even though that may be no help whatsoever in figuring out what you should do! I was a fairly early adopter of SACD and bought a SCD-1 and eagerly awaited the flood of new titles that would surely come with this clearly superior technology. The flood never even became a trickle. I had throroughly scoured the available discs and bought about 40, all of which sounded fantastic, and only about four of which contained music I actually liked. Eventually I sold the player and most of the discs and bought a relatively cheap vinyl rig (Rega P3 and Benz Micro Glider cartridge) and now have access to thousands of dirt cheap titles, albeit not a lot of new stuff. However, I live in NY and there are quite a few easy sources for records. If you live in the sticks it may make more sense to enhance your CD rig and forgo vinyl.

Bomarc makes alot of sense, but pragmatism is not always a strong suit around these parts. If it's any consolation, there are hundreds of cd tiles on ECM, CMP, Tzadik, Intuition, Hat, Enja and other labels that sound better than most SACD releases. Vinyl has its virtues, but it's often beat up and expensive when you can find the stuff you want. And it's FRAGILE! Don't let anyone kid you, a stylus does not ride the groove in a clean low friction environment. The contact surface area to weight ratio is about a ton per sq inch. A record isn't the same and doesn't sound the same after a stylus has been dragged through it a few times.
When you have an exceptional piece of vinyl, a great table, arm, cartridge, and stylus that are set up perfectly (they never stay properly set up for long) you can hear some %#@*/:>} GOOD STUFF!!. You can get way more than 99% of the way there w/ the best digital front ends. Sometimes the last .05% or so really matters. I think groovier'n hell that some guys go at it that way all the time. Unfortunately, they'll miss out on most of the incredibly good music and recordings that have come out in the last 10 to 15 years.