PC-based simple sound mixing with external hardware controller?
 

Need to play some video off of my PC with sound, and at the same time mix it live with the sound feed from the wireless lav at the venue.

I'm thinking, instead of bringing large/heavy standalone analog mixer, why not mix in PC itself?

Maybe I should feed the wireless receiver into PC's Line-in, and use some external controller to drive the volumes of Line and Wav inputs in PC's Windows mixer?

Is there such a controller with 2 knobs that'd be small, not taking too much PC resources (hey, video is playing!), and under $60?

It might be possible but I'd think it pretty risky - latency and CPU loading can pop up to bite you on the backside at the most inopportune times. Plus I'm not aware of any control surface on the market in the price range you mention - $300 for a Behnringer B-Control BCF2000 is the cheapest I know of. You could get a servicable analog mixer for around $100 and use it to mix the wireless with the playback coming from the line out of the computer sound card. I'd expect that approach to be more reliable and something like the Behringer Xenyx 502, 802, or 1002FX (if you think you want FX) would be adequate, portable, and cheap. Simple is better.

Laptop analog sound outputs are often noisy and most are designed to drive headphones.
Using a couple of passive direct boxes with selectable levels of attenuation and a ground lift switch can help get a clean signal into an external mixer. They will also allow you to run the cables a longer distance if needed.
You could also use a USB or Firewire interface or mixer to get the audio output from the computer, although that adds another layer of complexity that you have to test ahead of time for reliable operation.
I agree with Steve, I'd use the computer as a source only and rely on an external hardware mixer for combining the audio sources and feeding the PA and/or recorders.

Thanks, I'll try Xenyx 502, hopefully it'll do.

It seems to be small and light-weight, unlike my awesome sounding but big and heavy Mackie 1202VLZ PRO...

ROFL, the 1202 is big and heavy? Try hefting my 1642! :) I've actually considered getting one of the little Xenyx 802s for those times when I don't want to use or risk damage to or theft of my Sound Devices 442 field mixer and don't need the capacity to justify lugging around the 1642.

Suum cuique...