Make sure you do NOT buy the MX-850 from any place other than an Authorized Dealer. You don't get updatable software, nor do you get warranty or support from URC.

That means do NOT buy them from ebay.

I know you can get an MX-850 for as low as $200 from an authorized dealer (see my above post). For the extra $20, it's stupid to do it otherwise.

Yes, you can use the MX-850 IR only. No RF receiver is required.

I haven't seen a Sidekick in years. It was harder to come by than the MX-700.

You could use a cheaper learning remote...take a look at the Sony RM-VL710 (discontinued but on ebay) or RM-VL600. Use the MX-850 to teach discretes when necessary.