What to do about speakers?

I'm afraid this is another one of those "I'm building my first system and don't know a thing about how to do it - Please help" threads.
But seriously, after thinking about it and casualy scouting equipment for a few years I've finally started to build my first "real" system.
A little background first. (sit back and get comfortable this may take a bit) My wife plays the cello (not professionaly) and her father was an audio tech. with CBC Radio for years before he moved up to management and recently retired; so she has a well trained ear and enjoys good sound. I, on the other hand, do not have ears quite as well trained but am completely in love with music and enjoy hearing the little details.
That being said, we are just starting out (married only 2 years, she in grad-school me going into teachers collage) and so are not about to drop $??000.00 on speakers or the like.
Now for the meaty stuff.- I recently purchased my first piece of audiophillia technica - namely the much touted Rega Planar 3 turntable (yes he said P-L-A-N-A-R-3, not P3- it was the right price) and I'm running it with a dennon DL160 Cart. Yes, yes I know the speakers should have come first. But you see I've wanted the Rega for about 8 years now since I first saw one, so when I decided to start building my system I just couldn't ressit starting with it. Unfortunately this TT is being amplified by a (now grab a pillow to muffle your screams of abject horror) Marantz 2215 b integrated amp/tuner and, even worse, the speakers are from my highschool days and came with some cheap system I puchased at Sears. Before christmas (when I bought the Rega) I was using a pair of JBL-L112's but unfortunately they were not to surrvive the trip to the in-law's over the hollidays.)
So as I can no longer stand these speakers I am looking for replacements. My wife and I are currently renting and will probably do a fair bit moving around over the next 5-7 years so fitting the speakers to the room this system is in doesn't make much sense; suffice it to say it will be in the average sized living room of whatever average sized house we wil be living our average sized lives in. As far as price range we are looking in the $500-$700 range. I've done some reaserch, but must admit I'm quite baffled by all the speaker-tech that I come across .
I was thinking that a set of full range speakers was what I was looking for but then I realized that I don't know what the differance is between: Full Range, 2 channel, centre channel etc. is. So why would one purchase say a two channel speaker over a full range speaker?
I've been told(by my father-in-law and my hi-fi freak uncle) that the JBL S38 model would suit what I'm looking for, however, I thought maybe something like the Mission 701, or 761 series might be better but I really haven't the fainest, any help would be greatly appriciated.
Oh as for musical tastes, well as both my wife and I will be using the system say everything from the Beatles to Bartok, or the Smiths to Satie, or even Coltrane to Mahler.(Copeland to Guided by voices Anyone?)
And yes the amp will be next -but that's another forum.
Sorry for the ridiculosly long post and thanks to anyone who actualy read all of it. Thanks also in advance for your wonderfully witty, insightful, and incredibly helpful responses.
P.S. sory for any typeos:< ( oh And for anyone wondering It should be pronounced CHAS- when I registered it the name was taken so I had to be creative - ug!
Cheers.