There is also the bladeRF hardware, which is available
and in stock.
I have a unit and it is a very nice piece of kit. It achieves 40
MS/s @ 12 bit over USB 3.0. It uses a Cypress FX3, so even on USB 2
it should be able to saturate the bus. Unfortunately, the price went
way up after their Kickstarter ended. Also, the SW is still in
development and not polished yet.
Just to confirm, are you saying you can use the bladeRF as a proper SDR
like the RTL devices? I did look at it a while back, but to me it
looked like it required all the SDR processing to happen within an
onboard FPGA, so I assumed it wasn't a PC-based SDR.
Cheers,
Adam.