I had to look at the specs. That setup is about where I was 10 years ago.. except I had a single speed mulcher on an s300 that put out just over 30 gpm and not quite the same psi or nearly as efficient hydraulic system as the 650 has now. I think for what you are doing, with the variable torque motor, you will be okay but you are on the lower end and the motor will work hard to keep the pump up... at least that's what I can envision. I would have to check the badge on my 150 but if you are on the low end of the spectrum, I'd look at a 125 vt but with the 110cc motor versus a 65cc in case you end up upgrading machines.. That 125 or a 150 vt can go up to 40 gpm machine.
The 65cc motor in the new dml vt is slightly larger than my old 125 which, I think, was 63cc. Variable torque is definitely worth the extra money and if you get some cobra teeth it will work even better for you.
You will need a lexan door and debris kit.. not sure if the 650 has that kit but without it, you will have greater fire damage since these M series machines move a lot of air for cooling.
Do you already have the 650? If not, get at least a 750 or 770. Feel free to email me if you have any questions on how I set up my Bobcats.