SP-10 plus MC SUT or Baby with Bathwater?

For those of you who have followed my recent peregrinations, I am trying a whole new system approach- my existing Crosby-Quad, ARC-based system will become one alternative to a new, Avantgarde Duo/Audiopax Mono system. For now, I'm going to keep running my well-tweaked Well Tempered, and the Lyra Parnassus.
The question is the preamp. My SP-10 MkII has served me well, and is quite musical. It is not the quietest preamp in the world, and needs a step-up or other device for low output MCC, such as the Lyra P. My good friend George Stanwick, the importer of Sugden, has provided me, in a pinch, with a new phono stage from that company which is very quiet, but, obviously, I'm not getting the benefit of the sweet phono stage in the SP-10. I'm thinking, once the horns and new amps arrive, that I might want to do more with the preamp setup in this new system. One possibility is to go with an Audio Note Japan step up, so I can take advantage of the SP-10 phono stage, rather than bypassing it, as I am now, with the Sugden. My concern is noise through the very sensitive horn system, and also the obvious trade-offs of using this rather dated, but glorious piece of ARC gear with transformer, rather than buying the latest preamp/phono stage.
I've read quite abit in the archives here, and don't necessarily want to provoke yet another debate about the shortcomings of SUTs, nor do I want to spend the 20k dollars that seems to be appropriate these days for the best separate phono and line stages. I suppose for half of that, the top Supratek is a possibility, as is the Steelhead, and I've also considered in the all-in-one Aesthetiz Janus.
I'd love to continue using the SP-10 unless I am throwing good money after bad, so with my prejudices in mind, I'd invite some input. THanks in Advance.
FWIW ARC doesn't (didn't) recommend step up transformers. As I recall its in the manual. Personally, if I 'had' to have a low noise cartridge I'd get a different pre-amp w/or w/o a built in phono. I chose a medium output cartridge instead. Life is full of compromises, isn't it!