What cartridge to use....Rega RB25 Structural Mod

I have a Rega RB250 with the JA Michell structural mod and Incognito rewire mounted on an Acoustic Signature Final Tool. I am currently using a Koetsu Red with very good results. I am looking for something better. Aren't we all?? As you may or may not know, the Michell mod allows use of just about any cartridge made. There are 2 different counterweights. One for cartridges with a weight of 3 to 6 grams and another for cartridges with weights from 6-13 grams. The RB250 has an effective mass of 11 grams. So, with this in mind, what do you think. I am trying to stay within the $1,000.00 range, new or used. I have some cartridges in mind. The Dynavector DRT XV-1, XX-1, XX-2, ZYX Fuji R100 FS, Benz Micro LO.4, Lyra Helikon and the Ortofon Jubilee are some of the choices thus far. I have not listened to any of the above cartridges. I am going on reviews from this site and some of the professional reviews I have read. Please let me know if you've had any experience with similar setups or if you have any recommendations/suggestions regarding other cartridges I haven't mentioned. Also, I need to purchase a cartridge alignment tool. Any suggestions on tools under $50.00 would be great!!

Thank You
I'd recommend adding a "TWL mod" to your 250, at the expense of sounding like I'm beating my own drum.

Please check out the "Strange Tonearm Tweak" thread, here in the Analog forum.
Many have found this to be a very solid improvement, particularly with the lower compliance cartridges, such as your Koetsu. In fact, it would be perfect for matching your Koetsu to that arm.

Note that I no longer sell this mod, and it is easy to DIY for about a couple of dollars.

You can make it removable if you want(by using Blu-Tack as the adhesive), so you can do a "before and after" comparison, and remove it if you don't like it.

If you don't think it is a dramatic improvement, I would be quite surprised, as many others have called it "the best mod for the money, ever".
It wouldn't surprise me to find that it makes more improvement than all your previous mods.
It has found many happy users, all over the world, and on this site, and on AA.

Maybe when you start hearing more of what your Koetsu can do, you might not want to change it. And that could save you bags of money.
I have the Gyrodeck with the modified RB 250 Technoarm. I have had excellent results using a Van Den Hul Frog with this set up. You can find this cartridge used with in your budget. I use Wally alignment tools for set up.
I agree (sort of) with TWL – keep the cart and upgrade the arm. If you do have some money to invest, get a better arm and you will be shocked to see how much the Red can deliver.

IMHO you are already running into diminishing marginal returns by trying to upgrade from Koetsu Red on your RB250. The RB250 bearings are not up to scratch to extract the most out of said cart, even less so from a better cart.

(I am being kind by saying the RB250 bearings not being up to scratch – the bearings are total shyte)

Look into one of the OriginLive arms and then later a Shelter 901 cart. This would be fabulous combo. You'll at least find interesting and informative reading if you do nothing else.