If you had $2500 to spend on a new TT and cart.....what would you buy?

Technics 1200GR or 1210GR with a Grado cartridge!
https://www.technics.com/us/products/grand-class/sl1200g-series/sl-1210gr.html
https://gradolabs.com/cartridges/

I’m not a fan of NEW turntables and I’m super tired of Technics SL1200 series (been using mine for 25 years). The SP-10 mkII is better.

My advice is Luxman PD-444 because it can handle 2 tonearms (including a long one), it’s super easy to mount any tonearm and quickly adjust it without drilling plinth and all that stuff. Because it’s an amazing Direct Drive turntable. Because it’s an awesome design, it’s beautiful. And the price is only going up every year! I have two in my system.

Regarding cartridges you have to find which one is the best for Polka :) But spening more on turntable like Luxman you can spend less on a cartridge, because Stanton 881s is a champ at very low cost (something like $450-750 for a NOS nowadays) compared to more expensive cartridges. I hope it can play Polka very well . Same about tonearms, some great vintage Japanese tonearms available way under $1k ($700 Luxman TA-1 was an answer to Infinity Black Widow. It was made by Micro Seiki. you will see one in my system with Stanton WOS).

I've heard the unit before...and if my budget was $2500. 

I'd buy a Rega P6 with Exact cartridge...simple to set up, sounds great and has a lifetime warranty from Rega. 

For simplicity and good sound the Rega/Exact is a good choice. I would prefer the 1200GR paired with a Hana SL.