I've been using an SL1210M5G for 8-1/2 years and incorporated some tweaks along the way, each of which has made for a sonic improvement. Many of them, such as the tonearm wrap, better headshell, footers, and butcher block platform, lower the noise floor, minimize resonances, and as a result increase dynamic range, bass extension, overall linearity, better tonal balance, and inner detail.
KAB's fluid damper improves tracking and lowers the amplitude of the arm/cartridge resonance, enabling morre good cartridge matches.
The tonearm is hollow and has a distinctive high pitched ringing resonance. You can make this go away for next to nothing by wrapping it with Teflon pipe thread tape. It's only about $1.50/rool, and you only need about 18" of it.
The
LpGear Zupreme is much better. It has better wiring, the headshell is more rigid and inert than the stock Technics headshell, and it is also adjustable for azimuth. The
Sumiko headshell is very similar, but almost twice as much and not quite as good, so why bother?
I use a KAB record grip to snug the record to the spindle. It also audibly reduces noise, whether it's from the turntable mechanicals or record surface noise, I don't know, but it works.
The stock footers on the Technics are not very good. In spite of their serious look, they don't isolate well from room vibration nor do they drain internal vibrations from the turntable. There are many many replacement footers available, but the simplest and most cost-effective are the Vibrapod Cones, and are even better when placed on matching Vibrapod 2 Isolators. This comes out to $56 total. You lose the height adjustability, but I use small stacks of 3x5 cards to level the table. You can even cut the file cards into circles using a Vibrapod Isolator as the template so they're not visible.
Of course a good mat is important. My mat works very well but I can't realistically recommend it because I was just lucky. I asked at my local used audio dealer and they offered me an out-of-production Oracle Groove Isolator, a heavy sorbothane (but *not* sorbothane gel) mat that effectively drains record noise and isolates the LP from internal mechanical noises. However, you have a lot of choices, and those leather mats intrigue me.
I actually place my Groove Isolator on top of the felt slip mat that came with the turntable. It sounds slightly better and significantly damps the platter's tendency to ring compared to the Isolator mat by itself.
You can further isolate the turntable with a butcher block cutting board. The thicker the better. I started off with a $20 one from Ikea, but later moved up to a massive 3-1/2" thick maple butcher block one. Normally these are $200-300, but I got mine from Overstock.com for about $100. You can further isolate by getting a pair of silicone gel keyboard wrist rests from an office supply store. I have my butcher block resting on a pair of these, which run the full width of the cutting board.
You can see my turntable setup
here.