Best entry level VR video card?

I would go with the 390 overall but there isn't a huge amount in it.

Is there any 390x cheap or even a cheap 290x used.

Nope. GTX970 or R9390, kind of a crapshoot at the moment, without concrete evidence (i.e. VR game benchmarks, DX11, DX12). Even then, driver maturity will have a large impact on performance.

I'd be as much undecided as you TBH, with a preference towards AMD at that budget.

I go from NVIDIA to AMD, almost on a rotation (560ti, HD6950CF, HD7970GHZ, and now a 980ti), so not really biased, and no bones to pick with either, although I would acknowledge that games are often biased towards NVIDIA in general, and NVIDIA has a more energy efficient design (cooler, quieter).

But for VR, it's gonna be a different ball game.

Depending when your VR headset is due it may be worth waiting for Polaris/Pascal, either get one of them or pick up a cheap previous gen card when they drop the prices to shift remaining stock (I got my 290x's as the 390x came out, I can sell them for more on ebay now than I paid for them as I bought at the right time).

You can try to find an AMD R9 290 used. I see ebay auctions going for around $200-250.

Thanks guys. I'll take a look at the 290 but I've never bought anything off of ebay.

edit: and I'm likely getting one of the earlier shipments of both the Rift and Vive so I won't be able to wait long.

As above a cheap used 290 makes sense, to buy a new top end card right now with the next gen cards so close would seem a bit of a waste.