Shadowhywind - (boy are you in for it!
) - but you're going to have fun! This forum is your best source for information. Read the sticky tips & tricks!
Since you're starting - remember to keep copies of all of your orders, receipts, and packing slips - scan them in to a folder and include that folder in your back-up routines.
When you talk to X10, tell the nice sales folks what you want and most of them will find a "package" (past or current) that will give you the best price. Also, look on ebay for guys who sell a lot of stuff. 1's and 2's are ok, but beware the seller's warranty.
What Mr. Sullivan wrote contains an important piece of data. If you use OnAlert (plugin) you can then use the security sensors as 'triggers" for macros, BUT the macros will ONLY run if the PC is on - macros triggered by security sensors cannot be stored in, nor run from the CM15A.
However, as he also pointed out - The V572RF32 from WGLDesigns converts RF from security sensors (and remotes) into user-defined PLCs. PLC triggered macros CAN be stored and run from the CM15A without a running PC. The V572 is also a "whole house" transceiver. Its range is great! An un-modified CM15A sometimes has less range than you can spit.
Since you're just starting, read about Jeff Volt's XTBIIR. Read, ask, read, ask - there are some guys here that have been doing X10 since Thomas Edison was in short pants.
Welcome to the club!