Relative Spending on Turntables and Cartridges

Percentages are meaningless. No one is talking about the phono stage. Critical part of the equation. Arm is most important. I had a P5 and upgraded the RB700 arm to the RB880 and was BLOWN AWAY. Then upgraded the table to the P8 which was nice, but not anywhere near the difference. Then I got a Sutherland phono stage (was using the phono section of a Plinius integrated which has a switch between MM & MC), which can match to most any cartridge which also made a VERY NOTICEABLE difference. I happen to have a van den Hul MC ONE Special that I got a very good deal on used from a dealer that lasted 9 years because of its unique stylus and was replaced very reasonably because of their service/shipping to the Netherlands being hindered by Covid. I wouldn't spend over $1K on a cartridge. They are disposable.

Just my 2 cents. If your P3 doesn't have a PSU, that would be a big help for speed consistency. Not sure what your budget is. I'm not sure if Rega will sell the RB 880 stand alone (my dealer was desperate for business so he took it off of a P8 and then sold the P8 to another guy who wanted the best Rega combo (before the P10 came out) and the dealer sold him the RB2000 arm). Now they have an RB 3000 that comes with the P10 that they don't sell by itself. Problem is, now you're over $5K for the P10 table which opens up a lot of other possibilities where you can take a Rega arm and put it on a different armless table that may sound better.

I did it step by step so it was less painful, keeping each step under $1K (except the P8 part was a little over $1K after trade in). Problem is, they do add up after a while. As long as you have an idea where you want to get to, don't waste money on half measures (nod to Breaking Bad fans). It's OK to have one piece substantially better than the other. I got the MC ONE special on the P5 with no external phono stage because as the dealer said, it was a "unique opportunity". 

For you, IMHO I would start with the TT-PSU $350 I think, then the RB880 arm, around $1000 after you trade in the RB330, then a phono stage if you need it (you can get a good used one under $1K), then a cartridge, which I would wait on until it wears out and then revisit that.

It's a journey....I like hearing each incremental improvement rather than a big bang.

My thoughts:
It’s a matter of where diminishing returns cut in most steeply, and what your budget is.
For a $5-10k setup, diminishing returns for turntables seem to be about $4k, and $1500 for cartridges.
For an under $2k setup, the figures seem more like $1200/800.
For the real pricey stuff, I don’t know.
Phono preamp prices are all over the map. I only have experience up to $3k, so you’re on your own for that. My ratios are $4k, $1.5k, $3k for table, cartridge, phono pre for 2 different systems.

I recently installed a lightly used Lyra Helikon MC cartridge (rebuilt by Lyra in 2016) on an old Planar 3 (early 2000s) that has some modifications. The sound quality was spectacular. Placing the turntable on EVP footers was an additional improvement.

What kind of arm on the Planar 3 vinylvalet?

FWIW , last night I was finally cleaning out my audio closet .
WAY in corner down below I found a Shure M91ED new in box I did not even know i had . Slapped it on a low mass arm of a direct drive .(I’m good at alignment ) and dam near fell of my chair as it sounded every bit as good as the 1200 $ number on my Rega P6 and tracked better !

My mind shifted back to the Glory Days of the 60’s which I wasn’t thinking of because I did not want to recall what Companies like Empire, ADC , Stanton, Shure, and many others were making .The box on my Shure still had the price on it . 21$ .