Does the ARC LS-17 sound thin?

I bought an ARC LS-17 in beautiful shape from the original owner to tide me over while my Counterpoint SA-5.1 is back at Mike Elliott's place for the final power supply mods.

My impression of the LS-17 is that it is a very clean sounding preamp from top to bottom. However, I do think that the upper bass and lower midrange is shelved down which makes the bottom end and upper mid-range and high end stand out in relief. To my ears, this gives the LS-17 an overall thin sound in comparison to other preamps that are more fully fleshed out.

I would like to know what the opinions are of people that have owned the LS-17 and since have moved further up the ARC food chain. Do you agree with me? If so, how high up the food chain do you have to go in order to have the missing meat put back on the bones?