A soliton jnr would probably give you the best control, and let you "abuse" the motor at lower RPM without allowing full current at higher speeds. It can't do regen however, and is a very big beast for 40kw peak (50kw will burn the motor fast - however you can allow 450A at lower speeds for very short durations).
A Kelly KDHE 600A would be the most cost effective way to run it, and will certainly provide the power required, though as mentioned above quality control and support are not anywhere near the levels you could expect from EVNetics. It will support regen however (though this is of marginal use in racing, since you don't want to be heating the motor/brushes to brake as well as acellerate fast - it will just lower the average power you can use during a race ultimatly). I have most experience with these Kelly's on Agni's, and can say that if your lucky enough to get a controller that all the features work on it will probably do fine - but they are not all equal! There are a number of race bikes out there that still have KDHE's fitted and are working fine after several years abuse - but we went through a lot of support/RTB's to get them stable..
I've no experience with the Synkromotive controller at all, and none of my customers have ever reported its use with an Agni - you'd be on your own there!
Bear in mind that both the Syncro and the Soliton were designed for series motors rather than PM motors, though I've had at least some experience on the dyno (with Agni's) with the Soliton and it performed well.
An Alltrax (with a dongle to convert speed throttle to current/torque throttle) would be a good fit here - however they don't make a 100v capable model
No ideal choices out there yet in this power bracket..
Regarding power levels on the 111rdr motors, it must be remembered that although these are powerful and efficient motors, they have very little thermal headroom. If you plan on running it too the edge (it sounds like you are) you must have proper thermal protection (aim to keep brushholder temps below 95C), and work your levels up slowly as you refine the cooling arrangements and tune the controller.
Hope this helps!
*Mazda MX-5, Soliton 1, 300v 11" Kostov, 21KW/h Turnigy Lipo. 1050KG.
*Hudson Kindred Spirit 3 wheeler, twin Agni motors (70KW), 5KW/H pack. 300KG.
* +Lots of electric motorcycles!