These are both great amps. I have had more listening time with the Luxman SQ-38u, which is a great amp but expensive IMO. I have only heard a couple of demos with the Leben CS-300, and it was also a very nice amp but it's hard to compare amps heard at different times and in different settings. If I was pressed to pick one for myself, it would probably be... either one.
If you are looking for integrated amps in this genre you have other great choices:
1- the Audio Note Oto is an excellent integrated SET tube amp (it's my personal favorite), and it's quite reasonably priced on the used market. 12 Wpc; it's available w/ or w/o an integrated MM phono stage.
2- the Conrad Johnson CAV-50 is wonderful 50 Wpc PP amp. Very sweet sounding and is also quite reasonable on the used market.
3- Shindo Cortese and Apetite 6V6. IMO, probably the ultimate line of amps in terms of build quality and musical tonality. But you have gotta love green!
Finally, since you are also looking for speakers don't be worried about the relative power ratings for these units. In a moderate sized room, 10 Wpc is plenty if paired to the right speakers. As a general guideline, I suggest that you look at speakers that are 92db or more efficient, but I have paired SET amps w/ less efficient speakers in a small room and it has sounded fine. But not all speaker/amp combos will work - if possible, try before you buy. This is where a good dealer will be very handy.
If you are looking for integrated amps in this genre you have other great choices:
1- the Audio Note Oto is an excellent integrated SET tube amp (it's my personal favorite), and it's quite reasonably priced on the used market. 12 Wpc; it's available w/ or w/o an integrated MM phono stage.
2- the Conrad Johnson CAV-50 is wonderful 50 Wpc PP amp. Very sweet sounding and is also quite reasonable on the used market.
3- Shindo Cortese and Apetite 6V6. IMO, probably the ultimate line of amps in terms of build quality and musical tonality. But you have gotta love green!
Finally, since you are also looking for speakers don't be worried about the relative power ratings for these units. In a moderate sized room, 10 Wpc is plenty if paired to the right speakers. As a general guideline, I suggest that you look at speakers that are 92db or more efficient, but I have paired SET amps w/ less efficient speakers in a small room and it has sounded fine. But not all speaker/amp combos will work - if possible, try before you buy. This is where a good dealer will be very handy.