I have a setup with a really CHEAP laptop (An old Win 7 Dell that was $80 in almost new condition), one of those little 13" ones and a couple of the cheaper SDR's (SDRPlay and a Cross Country SDR4+) and it works pretty well. With the stock laptop battery, it runs about 4 hours before it starts warning me it's about done. If I use the car power jack (Totally fine if the car is off), no time limit applies. The laptop's speakers are well, not great, so I use a BT adaptor to listen through my car's speakers. You have to watch the volume closely though, it can get loud sometimes when you don't expect it.
The only real problem I was having was with the SDRplay and RFI. A metal Ebay case got rid of about 90% of it and most of the rest was taken care of with ferrite chokes on the USB cable. Any noises left, I can ignore. I've had shockingly decent results parked at a railfan park and a piece of coax going from the SDR to a fence and just wrapping the insulated center wire around the fence poles a couple of times. Any direct connection just totally overloads, and the nearby FM station suddenly reproduces itself along with several Aircraft and Wx transmitters. I usually just run an FM trap anyway, but it's not enough to keep things under control with an actual connection to the fence.
Right now, the SDR4+ is having a problem with a bad solder joint. I need to open it up and see what's going on. Smacking it is getting old.
