Buying another kit instead of 8293-1: Motor Set? I want to get some motors but don't know if it is a better idea to buy 8293-1: Motor Set or try obtain motors from some other sets. Is there any kit challenging 8293?
You have several alternatives, and you can combine several approaches if you've got the cash:


You can buy individual Power Functions parts from a LEGO shop or from various other vendors. The advantage is that you'll get the specific parts that you're interested in. The down-side is that it'll probably cost you more than buying a set like 8293.
You can buy a bundle from eBay. Several vendors make up their own kits that are similar to 8293 but with a slightly different mix of components.
You can buy a set that contains Power Functions. This tends to be fairly cost-effective if you're interested in the parts that the set contains, but with the disadvantage of a larger initial outlay. Of course, you could re-sell anything you don't want if you're prepared to put in some effort. The other advantage of buying a kit is that you'll probably learn some new techniques during construction.


If you go for (3), some of your options are:


8110 Mercedes-Benz Unimog U 400
9397 Logging Truck
9398 4X4 Crawler
41999 4x4 Crawler Exclusive Edition


Personally, if had the cash, I'd go for a 41999 (assuming it is still available). It includes a great selection of Power Functions components including remote control and IR receiver, a lot of generally useful parts, several exclusive parts (perfect for eBay?) and... well, it's just very cool.