Personally I think it makes sense to start with a pre-built radio to learn the radio technique and have something to compare with, but with an oscilloscope you can probably hack a kit into doing something useful. (I have the Softrock RX kit. Works well to receive WSPR.)
I've got a half-finished Ensemble RxTx that I'm super stoked to finish building. You don't need a scope to build it, but I've got one and it's really really cool to be able to look at the oscillating LO.
The only downside to the Ensemble RxTx is the sound card requirement. I'm probably going to order something right away here, but if I could have a do-over, I'd probably go for a Peaberry: http://ae9rb.com/index.php?main_page=product_info&products_i.... They were out of stock when I ordered though.
The book takes you through the basic theory, backed up with experimentation while building the kit. You just need a a scope and function generator, and of course a soldering iron.
There are web guides at that site for all the radio models.
It doesn't drift much and is reasonably sensitive enough. To keep ground loop hum out I ended up putting in audio isolation transformers between the radio and the computer, life probably would have been easier with laptop, and audio xfrmers don't work so well at 192KHz so that limits performance.
I've been thinking of buying a 455 KHz Lite model to help align tube radio IF strips. Like a cheap spectrum analyzer. In my infinite spare time LOL.
Life is a lot simpler now with the web frontend store, although the prices are around twice as high as the old yahoo group days. Used to sell the Lite kit in the group for like $9 years ago although batches always sold out in about an hour, which was annoying.
There is probably an interesting startup lesson that saving people 50% purchase price doesn't help if they can't buy it at all, friction in the sales process etc.
Personally I think it makes sense to start with a pre-built radio to learn the radio technique and have something to compare with, but with an oscilloscope you can probably hack a kit into doing something useful. (I have the Softrock RX kit. Works well to receive WSPR.)
73, KD2DTW