I was in a similar position as you recently, with much of the same "tasks list" that you have here. The difference is that I already had a 50hp 2wd JD 5103 with FEL and attachments. That actually helped me see that I needed something bigger.
I would suggest getting nothing smaller than a 60hp tractor. That will enable you to really grow into the tractor as your needs diversify and grow in the future.
Just like you, I was really set on buying something in the used market. I have never purchased a new vehicle, because I like the economics on the slightly used vehicles a lot more. I've never been burned buying a vehicle with under 30K miles, and I've saved a lot of money. So I was pretty set on NOT buying new when it came to a tractor.
However, as I started researching, I was finding that most used tractors that I was looking at were not really all that great of a value. I was looking for a 60-75hp open-station tractor with FEL and rear remotes in MFWD. Most of the nicer tractors I could find had 150-300 hours on them and I wasn't that impressed with the prices.
So I went to the local JD dealer and got a quote on a brand new one. It was basically $3K more to buy something with ZERO hours (vs 300) and that I would be the only owner of.
I kept my 5103 in my shop and in really good condition. It's hard to find used tractors out there who have had the same kind of owner as I am. Most of them were really "sunkissed" and looked pretty well worked - even for low hours.
With John Deere doing 0% for 60mo, I decided to buy something new. When I made that decision, I built the tractor just to the specs that I wanted. I'm very glad I did this, as I plan to use this tractor for a good while, and can't see a need for it that it would not fit in the next 3-5 years.
Just my $0.02. Here are the threads I started in debating some of the very same things you are wondering about here. Maybe they can help you sift through some of the thoughts / ideas / questions you have.
Help me choose my next John Deere tractor
New John Deere 5075E Open Station w/PowrReverser package
New 5075E with PowrReverser Delivery
***NOTE: The JD 0% for 60mo on utility tractors ends in 2 days - October 25, 2013.
Also, I am in no way saying "You need to get a John Deere E series!" There are a LOT of great utility tractors out there to choose from. The JD 5075E is the one I decided on that works best
for my needs.
Let us know what you come up with, or if you have other questions! :thumbsup: