I have no issue with the fan noise from my 663xB supplies.
The 6634B doesn't come up for sale on the used market that often, at least not here in the UK. They seem much less common that the 6632B (0-20V @ 5A) which is quite readily available.
I do have a 6634B, though, and it's very good at what it does - but the 1A upper limit is unfortunate. Ideally I'd like a 6633B (0-50V @ 2A), but I've yet to see one come up at a reasonable price anywhere.
The 663xB series can also work as electronic loads. I regularly use them in this mode to test battery chargers.