Need help with new surround speaker setup

Hi all, I'm having lots of trouble with this, so thanks in advance for any advice. My parents want to install surround sound in their media room. It's an oddly shaped room, and they want a balance between sound quality and aesthetics (no wires running amok). They aren't audiophiles, but they don't have a budget and want components that sound great and won't need replacing in 5 years. They've got a nice 50-something inch lcd tv with hdmi and a ps3 for blus, but no speakers or receiver.

So my first concern is about speaker stands vs. in wall speakers vs. angled wall mounts. I need to figure that out before even shopping for the speakers. Here are the room's dimensions:

width: 205'' (17 ft)
length: 228'' (19 ft)
ceiling: it's angled up (maybe 110 degrees?), flat for a bit, then angled down.
at the top: 131" (11 ft)
at the base of the angle: 89" (7.5 ft)

An artist's rendering of what it almost looks like (the 11' should be 17'):


We can easily wire the short walls for in-wall speakers, but it is not possible for the window and door long walls. The ceiling would also be easy to wire.

So, the room is an odd shape, and they don't particularly want to move their couch away from the wall. Would in wall speakers still sound good? Would it completely mess up the sound to put in wall speakers behind the couch? Would angled speakers sound better? How about ceiling mounted? Small speakers or bookshelves? I really don't know where to start. Price isn't an issue, and they want great sound without wire clutter. They don't want to upgrade in the near future, so an arrangement that supports 7.1 and possibly 9.1 would be perfect.

If you recommend a certain type of placement, what speaker brand/line would you recommend with it? I like Polk Audio quite a bit, but I'm open to every possible setup. I don't know what kind of speakers are required for such a large room. They'll need a subwoofer as well, and I apologize since I know this isn't the forum for that.

I know that was long-winded. Let me know if you need more info, and thanks again for any suggestions!

I appreciate the feedback. Since I can't put in-walls on the sides, it sounds like the rear should be wall mounted or on stands. Hopefully they can concede the couch position, and don't mind having stands all over the room.

For 7.1s, the two directly behind the couch could be in-wall, and not detract from the sound at all, correct? Then mount the sides and get a matching set for the front like you say. I know they would prefer only in-wall speakers if the sound were decent, but without being angled, and at such a great distance away, it seems like the sound quality would be poor.

Thanks for the dual subwoofer recommendation, I hadn't thought of that as an option. Are in-wall subs acceptable?

Is there a good site with pros and cons of in-wall speakers? I still haven't made up my mind if the sound quality gained by stand mounted speakers is greater than the aesthetic cleanness of having everything in-wall.

Also, would the small 'tweeters' be acceptable for surrounds in a room this size, or are bookshelves definitely required? I'm liking the Monitor 70s a whole lot for the Left and Right, thanks for that suggestion. Would two PSW505 12 inch powered subs be overpowering? The reviews on the 70s say they are fairly bass heavy to begin with.