Curious about the choice of cartridges. The Ortofon is nice, but entry level MC, the Digitrac is a nice low/mid end Ortofon, and the Technics may be the best P mount ever made, but will still need an adaptor, which won't be perfectly ideal. And the latter two may (or may not) be a great match for the arm - mass and compliance matching is not a cut and dried issue, and many implausible combinations sound great. I'd try the Technics. If warps and low end stability are an issue, I'd try a low mass headshell. The Orsonics apparently is low mass/low resonance, but it certainly is high expense. So try a cheapo headshell to see if it solves the oscillation problem before blowing a lot of cash on something that may not solve the problem, and consider buying a lower compliance cartridge - you can probably sell the Technics cartridge for good money.
