Some Direction Please......

Hi Leo first of all it seems like you're off to a very nice smart that Rogue/Harbeth combo should be excellent. On the subject of your next move I would suggest waiting for your new cartridge to arrive and listening for a bit before upgrading anything just yet. One point the Grado outputs 1mv cart so I'm not 100% sure would need a sut with it but I am certainly no analog expert. If you feel you may slip off the deep end into LOMC then certainly you may want one now or eventually. Also you didn't mention cables how is your system wired?

Hello,
    I'm sure those Harbeths are divine. And,of course, anything by Rogue is sure to be a quality piece. You are off to a very promising start. 
    A few years ago I purchased one of the ultrasonic record cleaning machines and it was like getting a serious upgrade to my whole analogue chain. Now that the newish Audiodesk Systeme Pro is out, there may be some good used Audiodesks out there. 
    Also, a small, quality, sealed subwoofer might just fill in another octave of depth without taking away from the Harbeth's brilliant speed and clarity. 
~Oran

Completely agree with ultrasonic record cleaning. In addition to immediate sonic benefits, it prolongs stylus life.

When you upgrade your analogue system, the correct order is turntable (for sonorous sound), tonearm (for repeatable adjustments), step-up transformer (if you are getting into LOMC), and then cartridge. I did it the other way around, against expert advice, and wasted too much money.

Thing is, cartridges wear out. Styli wear; suspensions wear, etc. The other three components set you up for the duration, and they don't break. Spend your money there first.

I used to have the rogue Cronus magnum II with the kt-120 tubes,  wry nice tube amp. Heads up, if you have 4 ohm speakers, make sure you change the internal wire that sets up the rogue to 4 ohm load, it made a huge gain in driving my Usher MD ii’s. 
For the Grado cart, I’d use the the internal mm phone preamp of the rogue. Btw: I tubed rolled  all the tubes (except the kt-120’s) which improved the SQ.
if you want to use the MC20, get a step up transformer. But im not sure if I would spend the $$$ to use the mc20, I’ve owned both the Grado and the mc20 in the past. 
In the end, the rogue just couldn’t control the bottom end (a little wobbly bass) so I went back to SS. For tubes, with the better tubes for the preamp and phone, the rogue is very very good

Thank you all for your comments. I was beginning to think no one would as I am certainly not in the stratosphere realm with my components as many of you seem to be. 
A few things I didn't mention. I do have a Loricraft record cleaning machine which is very similar to the Keith Monks device, though I've yet to use it as the plinth was ruined by exposure to moisture. I need to get around to building one out of some figured cherry or oak. I have the woodworking  equipment and knowledge - just not the time.
Also picked up a 'Spin Doctor' record washing set, my thinking being that for any extremely neglected Lps (and a few of my older ones) I might acquire down the road, I'd run them through the Spin Clean first and then go over them with the Loricraft. I totally agree with ultrasonic cleaning being the current state of the art technology.  I do happen to have a fairly large ultrasound machine designed and used for cleaning mechanical device assemblies (disassembled carburetors, jewelry, etc.). I  had the kind of mad idea of mating the Spin Clean and it for LP use - a sort of 'red neck' approach for sure. It is large enough to accommodate an LP - even has thermostatically controlled heating function. I might just try some old LPs I got from a neighbor. Even have a bunch of 78s laying around somewhere. What's to lose?
The subwoofer suggestion has also crossed my mind, and again, I have a custom built stereo transmission line unit (uses two KEF B-110? drivers) that was used in my solid state system where I bi-amped it and  a pair of modified Infinity Infinitesimals as satellites with two Yamaha B-2 power amps. It utilizes a custom crossover that's passive on the top end and active on the bottom. Perhaps I could send the Rogue's fixed output to one of my old Yamaha B-2 power amps to use this for lower end enhancement.
Cables are another story. I just have some old braided Monster Cables that were run to the Infinitesimals. No modern power supply or wowie- zowie interconnects between components. I could use some recommendations here for sure. As I've been basically in audio suspended animation for 15 years or so, it sure is a shocker to see some of the prices for cables, power conditioners, etc!!
Thanx again everyone, and if inclined, keep the comments coming.

rbstehno;

I've already picked up some Brimar, Mullard, RCA, Raytheon,and Sylvania 12Au7s. The latter three makes all long black plates from the 50s. Been thinking about some Telefunkens as well perhaps for the 12AX7 slots.
What have you used?

"Redneck ultrasound..."

Around here, we call that DIY, and it is much admired. I use a similar setup. I highly recommend the US spinner from Vinyl Stack - it's a very well made, fairly priced item, made expressly for the purpose. Get a spare handle and a record stand while you are at it.

There are several threads on the subject here, one of them current, and a very large thread on DIYAUDIO. Lots of good information to start you on your way with a minimum of false starts.

Excellent helpful reference wrt the DIY thread. Who'd a thunk there'd be such a thread on this site!
Thanx