What are the optimal percentages for analog system

Thanks for your responses. It seems like I should start with upgrading the phonostage first. I'm looking to spend about $500 on a used unit.

If you're a Grado fan, with your current system I would first audition the Grado PH-1 phono stage. I've never heard anything better with their own cartridges. Next, I'd look at upgrading the turntable. The Well Tempered Record Player is a great, modestly-priced platform for Grado cartridges, and the Grado tracks like a champ in the Record Player arm. In terms of PRaT, the WTRP offers a somewhat different balance of strengths, with pacing its particular virtue but with still very good rhythm; like the Rega, timing is a relative weakness. After that, I could recommend the budget-end Statement Platinum1--the low-output Grado really does offer some refinements worth hearing.

Again. Think about the cartridge you want, then find the arm/table that can handle it BEST. Go to:
http://www.theanalogdept.com/cartridge___arm_matching.htm
for a nice explanation about cartridge/arm matching with examples. Maybe your table/arm will work well after all and you can upgrade that piece last.
What you have isn't bad, but why make a lateral upgrade? Maybe a better table/arm does less damage to your vinyl collection? Maybe it's quieter? Ideally, it should work well with your dream cartridge.
Regarding the phono stage, I think that should be determined by the cartridge you choose. For example, I read that the Grado cartridges sounded better with SS preamps than with tubed preamps. The same article/opinion also felt that MC cartridges sounded better with tubed preamps than SS units. And if you go with MC, you'll need to match the cartridge's output with an appropriate amplifier gain and step up transformer. If you stay with Grado cartridges, they make 2 versions, high and low output. I can tell you personally that with the low output models, your choice in preamps is not that vast. They need a preamp with at least 56db gain, and there aren't too many of those around. I have both versions of the Sonata1 and a Grado PH1, and I prefer the low output Sonata1.
With a MC cartridge, I think you have more choices out there between step up transformers and phono stages. But you should really make sure the MC cartridge mates well with your tonearm. Therefore...get an idea of your dream cartridge, choose your table/arm accordingly. Hopefully, the cartridge you have will work with your new table. Maybe your dream cartridge will work with your old table. It would be a shame to get the new preamp first, then have to toss it because it didn't match well with your cartridge. Preamp should be last. Cartridge vs table/arm depends on whether your dream cartridge will work with your present table.

the grado and belari are not good for each other. both kind of on the low definition, warm and fuzzy side; instead of balancing each others' weaknesses, they add to them. I had a Bellari and hated it, so that would be the first to go, for me.

I haven't had a grado myself but I have read in forums several times that they tend not to match well with Rega's due to motor interference, resulting in hum. That said the pickup's life's finite and you are going to replace it eventually anyway. Otherwise I tend to mostly agree with Elizabeth. The table is capapble of acommodating better gear at both ends. So I would say upgrade the phono stage first and get something able to work with both MM and MC carts unless you want to buy an SUT later as well (that in itself is not at all a bad thing, but it adds another element). For $400-500 used you can pick up a Lehman SE and they sound terrific, belt suspenders and a bag o chips.
Proportions are arcane to me, but I would guess 25, 25,25, 25 to be fair. Generally, and I may get spanked for this by some, I would stay away from used pickups only. Tables are also very tricky to ship.
Myself I went with a good pre with built in MM/MC phono and couldn't be happier.