[TenTec] 2nd Try: SDR Technology ?

[Rick - DJ0IP / NJ0IP]

First pass brought a lot of suggestions for SDR models, and I have an exact plan about how I want to attach the receiver to my Eagle, and manage it with N4PY software.  I have a short list of 2 receivers.  I may possibly be able to borrow a Flex 1500 for a couple of months and use it as a receiver. 

However, my fundamental question did not get answered, in fact not even really addressed.

"What technology differences do we compare when evaluating SDR receivers?"
(Let's stick with the low cost - under $300 -  for this thread please.)

Basically all of the SDR radios are sensitive enough.
I guess, at least for the low cost models, the selectivity is determined by the sound card.

I want to compare radios that have built in sound cards because I don't want lots of wires running to my laptop.
But what do I look at?
Do we compare sound card chips in this case?
If so, what specs of the sound card chip are important?

What else?

>From what I have been able to find on the web, all of these low cost models have a close in BDR3 ranging from about 65 to 75dB.  Not great but acceptable for daily use, at least in SSB.  Better receivers go for $500 or more.  No surprises there.

For my initial project, I will just use some simple stuff, but I'm curious to learn more about this technology.
It won't be too much longer before the theory we all learned is school is not even used anymore.

BTW, this is one of the best pages I have found so far on this topic:
http://www.rtl-sdr.com/roundup-software-defined-radios/ 

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)