Okay - you have the sub out, so that saves you having to buy an extra crossover.  Incidentally, do you know what the low pass frequency of that output is?

Unless your amp has a summing input (where you can provide a signal to only one input channel but have both outputs driven), you will need to split this output into two separate channels, to feed each input channel of your amplifier.  The sub out on your receiver is a female RCA, and you need to split this into two male XLRs.  You may be able to find just such a cable, or use a cheap RCA Y adapter with two separate RCA to XLR single channel cables, or just buy the appropriate connectors and make what you need.

As for the amp to speaker connection, you could just wire this directly (I think your amp has binding posts for this purpose), but personally, I would shell out a few bucks for the Neutrik Speakon connectors - that is the other output jack you see on the back of the amp.  One cable connector for each end of the speaker cable, and one input connector/dish receptacle for the cabinet.  If it is a permanent home theater installation, it doesn't really matter, but the speakons give you a connection that is tolerant of many cycles of connection and disconnection (important if you move your gear around a lot), plus it looks cleaner (if that matters to you).  The Speakons are bulletproof, and will accept up to 12 GA wire with no soldering necessary.

-Sean

Don't know about Radio Shack specifically, but there are lots of sources for both types of connectors.  Just do a Google search.

-Sean

Here is a site that shows the pin out of wire for making the cables.

http://www.mediacollege.com/audio/connection/

One more thing - given the option between a balanced or unbalanced version of a given cable, you probably want to use the balanced version.  The discrepancy arises because RCA is inherently a single-ended connector (i.e. 2 conductors as opposed to XLR's 3).  The potential for the chassis grounds of source and amplifier to float with respect to each other can lead to amplifier hum, for example.

Balancing may not be important in Bob's home theater, but there are other pragmatic reasons for using the XLR connections - maybe more important for PA applications than for use in the home, but still worth mentioning:

1) the XLR engages all of its conductors at once, and can not short circuit the signal lines during connection / disconnection

2) the XLR is a positive locking connector

Just a thought - if the amp has both XLR and 1/4" phone plug inputs, could you achieve the split by using a single RCA to XLR from the receiver to one amp input, and then use a 1/4" phone plug jumper between the two input jacks on the amp?

cabbies in romania don't carry guns...or at least i haven't met any
come by anytime
the stuff about xlr and other types is really useful. thanks for the topic guys. i hope bob uses this info

Actually I purchaced the LSA900 here.... http://stores.channeladvisor.com/musicsupplycenter/Items/100-01-0208?

But, I'm sure the inputs/outputs would be the same.

Bob