Buying another kit instead of 8293-1: Motor Set?
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.