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.
