First the axiom of tractors: You can never have 'too big' of a tractor or buy too much tractor stuff.
I bought a 3320 for 6.5 acres and thought that was overkill....

Since my 2305 did just fine on it. I've since traded the 3320 for a 3720 cab so I can't be one to talk...
My only worry is if it would be too big and do damage. If you bought it to mow 2.5 acres I'd say your in this category and you'll do more lawn damage than mowing with a 2305 or 2320, etc. If your doing 'tractor stuff' then I don't know, maybe it's not overkill. Maybe you need the height, lift capacity, etc. BTW: When I bought my 3320 I did the same thing, the 2520 was too expensive and too close to the price of a 3320 so I went for the 3320.
I have a 2.6 acre lot and a 6.2 acre lot. On my 2.6 the 2305 is more than I need. In all honesty it was more than adequate for the 6.2 acre lot when I used it there for mostly mowing and some loader work (I wanted a 2nd tractor to avoid transport and a bigger one for digging, stump grinding and just because. etc.). On the 6.2 the 3720 cab is overkill but I like overkill when it comes to tractors....
One other consideration is that if you plan on transporting it you'll need a pretty good sized tandem trailer to move a 3320 once you put a loader on (close to 1500# with the bucket), loaded tires (900# for the large R4's), and a
ballast block (1000-1100#).
One other thing. If you are going to mow with that, save your $$$ on the MMM unless you plan to leave it on all the time. Buy a cheap lawn tractor, zero turn, or RFM. The 72" 7 iron MMM cuts like a dream but is very expensive and taking it on and off get's old awfully quick if you want to to 'tractor work' (You don't want to bang up that 3k+ deck). I have one and bought an 84" RFM last summer - I will use the MMM probably just for material collection (leaves) in the fall now.