Ad 2: Correct, you will need a Datalink cable between the MX and the Beocenter. Datalink will provide remotecontrol of the TV through the Beocenter and the other way. This will ease the daily use. You can use a non B&O cable, but then you will have to press CD when changing tracks and AV TV when changing volume - a little unhandy IMHO. If you fit a splitter in connection with Datalink make sure that all 7 leads are fully mounted.
Ad 1: The obveous choice is BeoLab 2500, which offers the original design and good sound. There is brackets available for wall mounting the Beocenter together with BeoLab 2500. Besides the 2500 any BeoLab (1-3-5-9-4000-6000-8000-Penta-3000-4500-5000) is compatible with your Beocenter. It just depends on budget and taste.
Living room: BV7-40 mkIV + V8000, BL5, BL3, BM1 and BS9000. Bedroom: MX3000 and BL4500 on MCL2-AV. Around: PentaIII, CX100 and MCX35 on ML/MCL + MCL2-A, BeoPort and BL4 on ML, BS3300 + M75 as stand alone, BC6000 + BC600 and BT1100, LC1, LC2, Beo4, Beo5 and BL1000, BS2 and A8, EarSet2, Apron, Coffee mugs, Enamel Bagdes, Bath towel, Keyring, Books, Lots of miniature and the Bottle opener. Office: BC2300 + BL2500 and BS3. Summer house: BS Century.
Addicted? Oh no.... ;)