As some may know i'm a bit of a Valtra/Valmet enthusiast. So any questions just ask.
Ran a A95 with a Botex 10 tonne forwarding trailer and a A93 with a front end loader and winch on it. Driven an N series and the T with a roof mount and big forwarder. but no where near as much as the A. Used the 6000 and 8000 series as well, I'm quite partial to the 8000 series but wish for the turning circle of a 6000.
The A series are solid little 100hp tractors simple and effective. I think the biggest is just over 100hp. I use to have a 12" 1.5tonne chipper on the back of one and it ran fine. They work very well in the woods as they're small and nimble got some photos i can put up if you want to see. It did struggle to do road work with a full up 10t forwarding trailer on it. 6 or 8 it would work like a dream. As a skidder it worked a treat and as a general loader tractor as well.
Downsides is that the cab is a very tiny box and very bland although the radio and air con is very good. The seat spins around to the back but as its not a flat floor tractor the room working in reverse is limited.
As said do get rear wheel weights i had 160kg on each if memory serves. Get the assister ram for the linkage or the pickup weight isn't great. Do get the forest roof. Get in an A series and think if you use the thing with the twin trac set up in. If your a big guy like me then it would be a no go but if you will fit worth its weight in gold. If you find a valtra with twin trac on it's expensive as it's that useful. Upgrade the pump to the hiflow one as well and get the forest tank.
Just a note on side arms on a A series they're top link sensing and this can be problematic when attaching them Sometimes you need (or you really should have) an extra little plate to take the load off the draft sensor otherwise the thing judders up and down all the time. Due to the small boxy step cab the view isn't great, especially for verges hedges it's not so bad.
N series is bigger range of transmissions which offers load sensing pumps and somewhere just sub 200l/m of hydraulic if memory serves. Cab is a lovely place to be view all round is amazing. As you'll be going second hand it's the best of what you can find. Once your on N series they're lower link sensing and come Cat 3/2 linkage with quick fit hooks, so if you have old narrow implements they don't fit, but no issues with hedge cutters. I'm currently looking at a N134 Active for farm work. Oh what a lovely beast it is.
Down side is that they have a massive turning circle. Don't know why the 6400 were much more maneuverable by a mile. Make sure you guard the fuel tank they were made bigger for the UK market so when you punture it (and you will) more diesel to spill out and pay to have cleaned up.
If you want a general tractor then get a used N series a 123 or similar 120ish tractor will do every you need. If you want a very specific tractor then a new A series with the options you want on it may b the better route. You could always have put a JAKE frame and put the crane from your forwader on the tractor which means you can do a bit more with it.