Very nice XK.
The Monroe Load levellers will make the back end feel more stiff. If you tow a lot or load down the rear often I would consider that an option. Otherwise I wouldn't go that route personally.
The other issue that people have with that shock is that the rubber sleeve that protects the shock body from the spring (the unique part of this "shock") wears down and/or slips and the spring rattles against the shock body. This can be alleviated by using an adhesive or and/or more durable rubber in it's place.
You can also gain additional height in the rear by stacking more spring insulators. I have gone this route personally. I used 2 additional spring insulators on each side on top of the factory ones. Going with a longer rear shock will allow more rear droop with your lift, since ATM the factory shock is likely limiting droop. This will improve ride quality.
Bilstein makes a 0-1.5" lift 5100 rear shock and a 1.5-3" lift rear shock. I'd consider the longer one if you do go beyond your current lift in the rear.
In the front longer shocks are not necessary due to your particular lift.
What is your measurement between the center of your axle and your fender lip @ your current height? A strut spacer may be a possible solution for additional height in the front.
5100 "struts" (the front shocks) start @ a minimum of .75" increased height, and are adjustable for 1.5" and 2" as well, but if you use these with your current lift you will likely take your suspension beyond usable angles, and have contact in several places.
RC lift and 5100's are a no go. I tried, that setup has way too much down travel.
CV's boots rub on knuckle, spring seat hits knuckle and it looked like the steering tie rods bind at full droop. I drove it to and from the shop to get my tires mounted. It sat right at 23", but at full droop it looked expensive with all the contact and that's with the JBA arms. It would work with limit straps, but I would not want to rely on straps to keep from damaging all of the other parts. I think you could add some down travel by either using a few washers stacked on the stem of the strut or using the 1/4" spacer on top of the strut cup. I want to get it back on the road, I have had it apart three times now. I figured the OME guys have been running the stock length setup with success and the 5100's already add about 3/8" to the strut.
You can run the Bilstein 4600HD in the front, which are stock length, and otherwise the same specs as the 5100 shock, no issues with mixing 4600's and 5100's.