If money is not object, I'd skip the 400$ service myself and sell it cheap for parts if there are some parts still working well. For 450$ more you could get a new complete fork with 2 year warranty (DVO).
I have been riding a D2 Diamond and a D2 Beryl (same forks) for two seasons and liked them quite a bit. I just got a new one as a warranty replacement and asked Suspension Werx to adjust the OTT to the most sensitive setting and it feels soooo nice off the top compared to both previous Diamonds I was riding. How was yours adjusted ? I don't know if the new damper is any different from your older fork, but I don't think they've changed many things in recent years. They do, however, offer custom tunes now if you buy directly from them, so getting a Diamond D2 + custom tune could be another well-priced option. And they're supposed to be creak-free now (my MY18 and MY19 forks ended up creaking after 5-6 months - 2017 and 2018 CSUs though).
I also just bought a Helm MK1 Coil last week and will probably try this one instead this season (nice to have a backup fork in these times too) but it's too early to give feedback ; ) Were you looking for the Coil or Air version ? The damper seems well suited to bigger riders so at 225 you might be just fine on it. You'd need to get a heavier coil if going with that version, but the Air has received better reviews than the coil because of the easier to adjust spring rate. I'm right in the middle of their "standard" spring so I can't wait to see how the coil version works.
The MRP have received mixed reviews and forum comments from what I've seen. Maybe they're better now, but I would put it last on the list. There are a few threads on MTBR about those so if you haven't checked yet it might be worth reading.
That said, if I was going to pay msrp for a new fork today, I'd be tempted to get a Suntour Durolux because of the longer travel option (the others stop at 160mm for a 29er) , bigger stanchions and stiffness reputation. The longer axle-to-crown would work well to slacken my bike a bit for a given travel too, but it's something to look out for if you already have a tall front end or maxed out at the warranty-approved A2C length for your frame.
It ends up being at the same price as the Diamond D2 (around 800-850$cdn) if they still do the Upgrade program or their seasonal discounts. As with the DVO and Cane Creek, the Durolux has creak-free reputation, adjustable travel without additional parts and has got good reviews from many places. The Helm can be found at 20% off at JensonUSA depending of the version you're looking for, but it seems to be getting less available since the mkII has been out.
I don't know if that helps, but at least you'll have thoughts from a person with similar suspension options in mind. Cheers!