Hello Andrew and welcome to the Beoworld forum!
The Beosystem 1100 is very fine indeed
1. You can use the "tape" input with a 5-pin DIN plug to RCA converter, Sounds Heavenly makes good cables.
2. You can play MP3's via iTunes, then you can use an RCA selector box, so you can switch between Mac and CD-player.
3. The Beomaster 1100 is the "Hi-Fi" range of B&O products, at line with the Beomaster 901. A fine reciever. The Beogram 1100 is also a very fine record player for the B&O novice. The Beocord is one of the very first B&O Cassette recorders, it is okay, but there is no Dolby noise reduction. Overall a good system ">
You can use the Beoworld site and beocentral.com for reference on your system
-Søren
Beocenter 9300, Beogam CD50, Beocord 5500, Beomaster 3400, Beomaster 4400, 2 Beogram 4000, Beomaster 8000, 2 beogram 8002, Beovox S-75, Beovox MS150.2, Beovox RL6000, Beovox S-35, Beomaster 6000, 2 Beocord 9000, Beocord 8004, Beocord 5000, Form 1, 2x Beolink 1000, Beo4, MX3500, LS4500. Born 1993.