How important is the tonearm?

The arm should be somewhere near the table in value. With a $5,000 table, a $500 arm just does not make sense. And with a $3,000 cart?
Anyway I do not have an answer. This is confusing. If you bought such an expensive table, and cart.. why don't you have the dealer offer advice?
Was this an estate sale or something?
Anyway, the arm I would buy is a SME 309, with the thought of upgrading later.. to a V series. but that is not the arm you should buy..

Amandarae" what I should have said is that most designers try to keep The tonearm's mass has low as possible to avoid unnecessary wear on the grooves..

Actually, the mass of the arm has very little if any effect on groove wear and designers do not attempt to keep it as low as possible. The mass of todays arms is higher than it was in the 70s in general. Something like the Transcripters VESTIGIAL arm with its mass of 3 grams or less would be laughed at today. The SME 3 arm had a mass of something like 4.5 grams, the 5 is 12 or 13. Low compliance cartridges will not work well in low mass arms in general. The critical factor in groove wear is the shape and polish on the stylus. Long ago there was an experiment in which an LP was played several hundred times tracking at 3.5 grams with a high quality stylus; there was no wear when it was examined under a microscope. Badly polished styluses with irregular shape are the most danger to grooves. I remember it the 70s HIFI News had a cover showing the magnified stylus of a group of top cartridges; many were obviously misshapen. I don't know what todays would look like; better I hope, given current prices.

Scipo said

... most designers try to keep The tonearm's mass has low as possible to avoid unnecessary wear on the grooves.

I do not agree with that statement. What does tonearm mass have to do with tracking force, in and of itself? Tonearm mass is a the main determinant of resonance. Is there a difference in groove wear if the same cartridge was mounted on a Grace 707 at 7g and an Origin Live Silver at 14g, assuming that both were adjusted for 2g or tracking force?

The job of the tonearm is to hold the cartridge in the groove with the grip and determination of The Incredible Hulk while maintaining the finesse of Tinkerbell.

That table deserves either the Triplanar or Graham. My personal preference would be for the Triplanar. TTweights also has the Talea, which is expensive, but will leave you speechless, even with a "lowly" 103r. You should try to hear one even if you have no intention of buying it.

(fill in your own TV voice talking really fast for this last part)
disclaimers: I also sell Taleas, but have no association with TTweights, other than we both sell that arm. I've owned a Graham 2.2 in the past. I currently own and use a Triplanar along with a Talea. I don't have any association with Wheaton or Graham.