As a previous owner of an SN2 i can say that it is a very good amp and is much better than an SN1. What makes it even better still is a HiCap DR. What i would be worried about though is an asking price of 1900 Euro. Most that i have seen for sale have gone for around the £1500 (1700 Euro) and quite a few have gone for well below £1500. Depending on age, i would say that 1900 Euro is miles too much to be paying. For that much i would spend even more on an SN3, which is a better amp than both the SN1 and the SN2.
Some years ago I heard a friend’s SN1 and it made me want one, but it took me a few years to to save for it, by which time the SN2 had been released. I bought a demo model SN2 and loved it. IMHO the SN1 needed a Hi Cap to make it sing. If you are considering upgrading your original Supernait, why not go for the SN3 which is better again?
I don’t know where you live, but SN3s are going for half their original RRP these days, making them an absolute steal. I think you would notice a significant improvement between the SN1 and the third iteration.
I moved from a SN1 to a SN2. I found there to be an improvement. Still have the SN2 with a HiCap. As mentioned above, it does seem a little too expensive.
The SN1 has always been a “marmite” amp. The old forum had some acrimonious discussions on SN1 vs 202/200 with strong views on both sides. A HC makes a big difference, and I always used mine with a HC, subsequently updated to HCDR. I eventually jumped to 272/250 rather than go to SN2, though I did audition one. For me SN2 sounds very different and is a “better” amp, at least in hifi terms. But, whether it’s more musically enjoyable is very subjective. If at all possible, auditioning before purchase is advised.