The Harrels come in three sizes. The longest being the Magnum size, good for fitting in cases up to 2.9" in length. Which should be enough for 6.5 SE, however seating the bullet out to 80mm COAL (3.15") might need a little wiggling about to get it all into the seater.
They look like a nice bit of design. Virtually identical to the Hood presses, some of which have an intriguing feature, micrometer adjustment of any screw in FL size die for precise shoulder bump. Or take two screw in dies. or 2+ 1 arbor type die. I don't know which design came first.
Other such things also exist, I suppose the extreme prices are justified by the tiny production volumes and use of costly machining techniques, materials, and laborious assembly by reasonably paid workers.
Evo Enginering (AKA Tier One) do/did make a nice looking compact press in the UK, read a review comparing it favourably with the Harrel here:
A few years ago, small portable presses like this one were strictly the preserve of short-range benchrest shooters who have – for reasons I won’t go into here – always reloaded on the firing-point between matches. But, this is the way benchrest shooters extract the maximum possible accuracy from...
www.targetshooter.co.uk
Maybe also look at the Buchanan hand press,
Buchanan Precision Machine L-N-L Hand Reloading Press with Case
This is supposed to good for FL sizing of even magnum cartridges, in both force and gape.
TBH I started off with a Lee hand press which was/is quite capable of all duties for my .223, 30-30, 308 and 303, so I imagine it would cope with 6.5SE just as well. Once you have got the hang of the proper technique.
Oh, and the Lee Breechlock Challenger is a smallish lightweight (aluminium alloy) but strong thing that can be be bolted to a piece of wood then clamped down wherever you want it. I've only seen the RCBS partner (also aluminium alloy) in a shop. It looked OK but I didn't think it was anything like as good, sophisticated, or feature rich as the Lee Challenger. Not dissimilar price nowadays, but when I bought my Challenger some years ago as a second press to complement my big cast iron one,they were quite different prices, and I liked the features of the Challenger much better c.f. the Partner.
ISTM that the Lee price has gone up a little, whilst the RCBS has come down a lot. It used to cost as much, or more, than a Lee cast iron press, which made no sense. The Partner was only ever intended as a "partner" to a big press, for light duties such as decapping, neck flaring, seating etc. Hence the name. I think the Lee Challenger is capable of much more, every task, for less money.
Better surely to have just one, that can do everything, which I think is your intention.
The Lee breechlock system works well enough for me. For certain dies, not all of them. De cap, neck flare, powder etc. I tend to just have a few extra bushings, into which I screw the dies for a particular session, set them up the usual way, then use. They are taken off again afterwards if swapped for something else. Then the dies used on my bigger press which only takes the standard screw thread.