Speakers need to be placed close to back wall. Help

Guru QM5 v2. Great little banging speakers that demand wall placement. 

Can either the Buchardt or Larsen speakers really deliver big, medium sized room filling sound?

The Larsens can. I haven't heard the Buchardts, but I would say in general the best way to "room filling sound" with stand mounted speakers is to pull 4-5ft from the wall to create a deep soundstage in all that space. In your use case, that's not likely, so maybe not so much. In a smallish room, e.g. 10x12 bedroom, sure you can fill that with most any speaker. Low end may be on the modest side. 

The match between speaker and the room size and placement is pretty critical, so you may want to wait until you know dimensions and talk over furnishings and setup flexibility with your recipients. Hopefully the room isn't square, those are tricky and require a bit of finesse on setup(e.g. diagonal) to get the most sound for your investment. 

Cheers,

Spencer

All good advice, Spencer.  Many thanks.

Mofojo:  they look interesting, and the specs and few reviews are very promising.  Many thanks.

Any omidirectional or semi omidirectional speakers are exactly what you require. I'm UK based and use a modified pair of NVA Cubix speakers and the ability to almost fine tune the bass by moving the speakers proximity to the wall has to be heard, it's really quite something. I know there are some very well regarded American designers of omidirectional speakers and I am sure you will be astonished by their performance viz a viz traditional design.

Ps Steve Guttenberg did a review a year or two which was very positive re one the American designs