Just been through this process. I am also 6'4" and around 18 stone.
I looked at the Reba and the Manitou Tower - the 29er Minute has been renamed and I couldn't find any of last year's Minutes with 100mm of suspension. Moreover, as far as I could glean the 120s are not convertible to 100s ( althouth the 100s and the 80s may interchange). I also needed a 1 1/8th steerer, not a tapered.
As far as I could find out the Tower Expert's come with a soft spring and the Pro's with a medium spring and you and I will need at least a firm and possibly an extra firm. Even though the Pro is a hybrid air plus spring system, there seems a fair bit of anecdotal internet evidence to suggest that without the upgrade the spring will snap. The Pro's are a MARS spring and although the Manitou website lists the part number I could not find one in stock anywhere on the internet, neither could my LBS find any record of the part on their system, either by that number or any other, and Hotlines haven't responded to my emails. Finally, the 100mm Pros are out of stock in this country and last time I looked stock is not expected before mid June. Apart from that they look very good.
The Reba is available in 100mm but only in QR unless you want a tapered steerer - and even the tapered steerer maxle has now disappeared off the CRC website and only seems available in america. RS's website says that they have not produced any aftermarket maxle 29er rebas this year. I went with the Reba RLT QR on the basis that by the time I had waited for the Manitou, got the spare spring, if it existed, and paid someone to change it I would have spent much the same as the cost of the Reba. There is also a Recon Gold 29er QR fork which is a bit cheaper.
CRC also do a couple of suntours with 15mm axles, the 26inch version of the air sprung suntour raidon seems to get good reviews but I couldn't find much info about the 29er version, and a Marzocchi 44 which is heavily discounted and possibly un-coincidentally has had some fairly average reviews. CRC is also unclear as to whether it needs a spacer inserting to convert it to 100mm. I already had the wheels for my build and was limited to QR or 20mm without a new hub and a rebuild, so ruled out the 15mm axled forks as not cost effective for me but you may have more flexibility if you have hope pro hubs or haven't committed to a wheelset yet.
Available options for someone our size therefore appear to be the air forks i.e. Reba dual air QR, Recon solo air QR, Marzocchi 44 TST 15mm or Suntour Raidon 15mm in descending order of price.
Hope that is helpful.