Buy an Audio Research SP10 MkII or an SP11 MkII ?

The SP11 was too cool, clinical if you will, for me. I've been using my SP10II for over 20 years and nothing else has tempted me. Tubes are an issue, you need quiet and rugged tubes.

Growlar, FWIW, and as sort of a counter point to John's comments on the differences between the SP10II and the LS5, if you are really anal about hearing the last enth of detail and extension his advise is worthwhile. But if you want to listen to music which is well served by audio the SP10 is an excellent way to do it. Regarding the units phono stage noise floor I would agree that this unit is not the best for a very low out put cartridge, a medium one such as the medium out put Benz Glider is just fine. By the time I get noise on my phono stage with the Glider I'm way beyond overdriving my system and my room. Regarding the noise floor of the line stage, much depends on the efficiency of your speakers and input sensitivity of your amp. With efficient speakers (+90db) and high input sensitivity (.5v) the line stage noise will be noticible in a quiet room. IMHO, the only real downside of the SP10 is that its not easy to experiment with tube rolling - it is demanding of rugged, low noise tubes in the phono stage especially, less so in the line stage. Finally, if you like the sound of that D115, you'll find the SP10 and excellent match. I had one for a number of years.