morrisond,
I think Steve (jenkinsph) and I are right. If you are going to use the implements from your 5425 such as the 90" slowblower and purchase a 110" finishing mower, then you should go with the 4000 series tractor. The JD PowerTech engines in these tractors will give you the torque you need for these implements, plus the tractor will give you a longer and wider platform to wield these implements.
Which 4000 series is up to you or what your dealer thinks; a good dealer will steer you in the right direction. I think you can get away with a 4120 or 4320, but if do not want to worry about having enough PTO power, then go with the 4520 or 4720 like Steve and I have.
You can also use the standard rule of thumb that many TBN members use which is 5PH at the PTO per implement foot. Your finishing mower would be ~9 foot which would indicate you need 45HP at the PTO and the snowblower is ~7.5 foot equally 37.5HP needed at the PTO. Personally, I think these numbers are high for a finishing mower and snowblower, unless you are hitting some very heavy stuff. Remember that 30HP or 35HP at the PTO on 3000 series tractor and a 4000 series tractor is quite different in terms of toque/power(work); the 4000 will be more powerful at the PTO with the same PTO HP rating. Good Luck with your tractor shopping; that is always a fun time!