I disagree the RB300 isn't worth tweaking -- especially if you're using a Grado Platinum or Sonata. If you were moving to a cartridge that didn't match the arm, or you were moving up to a high res cart, then it would make sense to get a better arm, but the RB300 is perfect for a Sonata. I own this combo and it does very well together.
You can easily find an RB300 for $200 and substantially upgrade it for less than $350. You'll have a very nice arm for $550. I don't know how you came up with $700. Here's my list:
$23 Michell VTA sleeve from eBay Buy it now
$159 Michell Tecnoweight from Galen Carol
You have lots of options for rewiring:
$205 Incognito Kit
$139 Cardas Tone Arm Rewire Service using the same wire as in the Incognito.
Do it yourself using any wire you want. I wired mine for about $100 using Cardas 4x33, WBT ends and some parts from the hardware store (rubber hose, braided steel hose, and shrink wrap tubing).
You can easily find an RB300 for $200 and substantially upgrade it for less than $350. You'll have a very nice arm for $550. I don't know how you came up with $700. Here's my list:
$23 Michell VTA sleeve from eBay Buy it now
$159 Michell Tecnoweight from Galen Carol
You have lots of options for rewiring:
$205 Incognito Kit
$139 Cardas Tone Arm Rewire Service using the same wire as in the Incognito.
Do it yourself using any wire you want. I wired mine for about $100 using Cardas 4x33, WBT ends and some parts from the hardware store (rubber hose, braided steel hose, and shrink wrap tubing).