Realistically, will the Spendor S 3/5 work for me?

Sonically, though I have never heard them, I believe they are quite in line with what I am interested in. But it's their size and low efficiency that I am wondering about and how they would work with my amp and in my room. My room is 13x22x8, which is what, a medium to large sized room? My amp is a 50 watt LFD Mistral integrated amp, which is not a power house nor is it a wimp either. I listen to Jazz, Classical, Ambient, vocals. I don't listen to music all that loud really, usually kind of a moderate volume, not soft but not blaring loud either. My listening position is about 10 feet from the speakers (certainly not nearfield obviously). I would use them with a well integrated sub.

My question is, given my room and my amp, music and listening habits, does anyone have a general sense if they would work for me? I once used a small pair of Paradigm Atoms while waiting for a new pair of speakers, which are similar in size to the S 3/5, and was very pleased with them in regard to volume but then again they have an efficiency rating of 89dB compared to the Spendor's 84dB. I know I would have some limitations with volume and all that, but realistically speaking, would I likely be underpowering them, possibly suffering as well from the room size, which could make them sound strained or even closed in? I like a warmer, more natural and laid back sound but I'd hate for them to sound too closed in due to lack of power and my room. I know going for another amp would likely alleviate the problem here but I really like this amp and would like to not get rid of it. Any insight would be appreciated much.
I have a friend with a similarly sized room using Ls3/5s to good effect. He has a Quad pre/power rated at 100W, but it's rarely turned up very far. He has no sub !
I think overall the S3/5 probably would work for you, but I don't think you'll have much margin, so my answer would be a cautious yes. If you had listed rock music, I think I'd say no.
The sub will help a lot, particularly with respect to preventing the underpowered sound, since much of the power of an amp is required for the lowest frequencies, which are not reproduced by the S3/5.
My feeling is that those speakers will work for you. Marginally, as perviously noted by Seandtaylor99. Those loudspeakers are very insensitive. They have very fine mid-band presentation. The top end is slightly soft. Since you're using a subwoofer the bass should be fine. If you
really like the Spendor line perhaps you should consider the 3/1p. It is larger in size and is more efficient! Perhaps this would be a better pairing with your 50w int. amp.
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Thanks for the respones thus far, I appreciate it. My feeling was, as Sean and Kotta have eluded to, is they would likely work marginally. Viridian feels it just would not work, and I can understand this point of view as well. I must confess something. Right now I am in the middle of burning in a new pair the Meadowlark Swallows, their monitor version of the Swift and I just love them. I was torn greatly between these two speakers before deciding to go with the Swallow, so the S 3/5 has been in the back of my mind even though the Swallow's are superb. After reading so much about the S 3/5 and their midrange who wouldn't be dying to hear this speaker?

I had hoped to perhaps one day find a pair of the S 3/5 used and compare it to the Swallow and make a decision thereafter. But in time and through much research I began to realize that in all reality the S3/5 just might not work well in my situation. I thought I might pose the question to see if my thinking was right.

The Swallow's are fantastic by the way, what with their 1st order design, T-line and all, they have midrange magic as well. Definitely a versitile speaker, they are quick and have excellent attack, they can do all kinds of music too. Smooth and non-fatiguing and man do they disappear into a huge stage. I'd recommend them to anyone who likes the Harbeth-Spendor-Reynaud realm of sound. I once owned the Reynaud Twins. Maybe someday I'll give the Spendor's a try, for now though I think you guys have helped put my mind a ease a bit. Thanks.
They should work.

Our local dealer has one in his 13x18 x9 music room and it worked fantastically. If you are looking for an accurate sounding speaker, the S3/5 will be one of them.
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Oh, I definitely was planning on buying a used pair, then sell them if they do not work out and lose little or nothing at all. I might still do this, this way I will know for sure. Yep, thus the way of Audiogon eh!! The only thing I am scared of is they will work and I'll love them, and then still love these Meadowlark's and be so torn!!
While you're speaker shopping be sure to get some Spica Tc-60s. I like the ls3/5, but I prefer Spicas. The imaging is just amazing.
So many speakers, so little time :-) Thank heavens for the used market.