Let's back up. Which platter are you presently using? I am a huge proponent of sourcing the very best after-market bearing available and have done that with both. my hot-rodded Thorens TD124 and Garrard 301 but I also sourced heavier platters than the OEM on each. On the other hand, there is something magical about the OEM lightweight 301 platter and OEM bearing, particularly the grease bearing. Considerations boil down to the STYLE/character of the sound you seek. The heavy duty precision bearing and heavier platter produce a more neutral and arguable "cleaner, quieter" sound, the OEM platter and bearing provide a more propulsive and dynamic sound that may be noisier, but is more fun.
Let's go big picture though; neither the upgraded bearing nor the custom plinth is going to solve your problem. You have a feedback/isolation problem. Your loudspeakers are essentially overpowering your tonearm/cartridge/record interface. If you have a handy friend (or an available contractor) please try my relatively easy-to-implement trick of bracing the floor joists under your equipment rack from underneath. This can be done on a temporary trial basis. Try 4x4 vertical posts wedged as tightly as possible without unleveling your suspending floor against the joists. That said, this will not eliminate airborne energy overpowering your turntable isolation. At some point repositioning your loudspeakers and even considering a different loudspeaker (and subs) may be required. Many of us fixate on the loudspeaker when putting our systems together and end up with a speaker that is simply too large and emits too much energy for the owner's listening room. Then "we" wonder why the sound does not match ones expectations. We can call this the "Magico Syndrome". For example, in my relatively small room my Devore O/93's are perfect and their bigger brother, the O/96's, as much as I love them more in a vacuum (larger room) would do the very same thing in my room as you are currently experiencing.
But yes, I would never have chosen a DAS plinth. Greg Metz provided me with one and mounted my 301 in it when I bought my NOS 301 from him. I could not get rid of it fast enough. Luckily for me, Russ Collinson of Layers of Beauty was still building incredible custom plinths at the time. And please, try Stillpoints when you upgrade your plinth. You might try contacting Steve Dobbins of Xact Audio for advice. He offers his own design of 301 platter and plinth and is a huge advocate of Stillpoints for 301's.
