It hurt to pay for the pavers, but well worth it, should have done it when the house was built.
I looked at the pre Tier IV 4 Series before buying my L5740 and really liked them, but I was trading in my L5030HSTC so Kubota was the way to go, I didn't really look at the 3 Series as it just doesn't fit any of the needs we have another one won't do, but I they look to be very capable.
You mentioned buying a new one then getting an older big tractor which should work well, we have them made in the 50s, 60s and one in the 80s and they are used frequently, so that may well work for you if you can find a good one.
Good luck.