Allocation of analog resources

I don`t think that your request is too vague, but there are many considerations.
Your phono stage is quite good, IMO, so I would concentrate on turntable/arm/cartridge, and roughly allocate one third of your budget to each component.
There are also a lot of second hand bargains out there. Second hand cartridges are a bit risky, but turntables and especially tonearms are pretty safe to buy. You can`t go very wrong with something from SME or Fidelity research.

Balance is important to some degree. Your Lyra cartridge is a good match with your AR phono stage and if you get a new cartridge it should have output about the same as the Lyra.

A good tonearm is very important, and a tonearm costing as much as your turntable is fine. You will get more out of your cartridge with a better tonearm.

A used AMG Giro turntable might be a consideration for you. The AMG tonearm is an excellent tonearm

"something around $2.5-$4k for an arm"

If you're adventurous, using the VPI as a temporary home for a really nice arm is another option.
https://www.audiogon.com/listings/lis991g5-sota-satellite-series-ii-turntable-with-rega-s202-tonearm...

Something like this, in the 10" would be a huge upgrade on the substantial Classic base. 

As some are mentioning, I wouldn't be so concerned about cart. Looks like you have competent phono stage to grow with.

Kuzma will put all your existing carts and future in another league. The arm can eventually go with  the appropriate Kuzma table, or whatever you decide, if  you don't get both at the same time.

Classic 1 is perfect tweakie base. It reminds me of the Rega P5 which can be jacked to approach the stock VPIClassic 1. Classic 1 with a few thought out tweaks should approach something near $10K.

Stock the Classic 1 is weak without SDS/Phoenix. Perhaps you already have that covered as well?  Arm and speed control should elevate it considerably.

The Audio Research PH5 is a good phono stage I have had a PH2, Ph2se, ~PH5, PH8, and now a Reference 3. All great phonostages at their price points.

@ghdprentice 

I adamantly disagree with this statement. I do understand that when you do a purchase like this it feels like a huge risk. But in reality it is not. Moving up in cost by 10x… unless you do something terribly wrong is a virtual guarantee of a jaw dropping, wonderful improvement in sound. This is the quickest and surest way to awesome sound. You cannot do it blindly… but this big of jump covers minor errors.

This is an excellent point. I should have framed my comment that I saw as risky because I had never made this significant of a jump in cost before. I would have felt so guilty spending the money if I made a wrong decision and it sounded the same. However, it did work out well beyond what I expected. 

Thanks!