I've used the Konova and it is a really well built and smooth product. I haven't used the Varavon but they look very similar in terms of quality and function.

Varavon looks good, but can it do vertical movement or upside up?

I don't see any problems with both.

But I strongly suggest properly tuning rollers and use something to smooth vertical movement (I think it is same for every slider).

You can check V sliders at http://www.varavon.com/index.html

They are usually on deals once or twice per week.

You are right, on the IGUS you have to buy a motor, I´m going to do it, I bought the slider but is useless for now.

http://www.cameragrip.co.uk/acatalog/hps_hague_power_slider.html

@Kihlian

It is not Igus, check carefully. It uses same rails, but not same sliding base, as it has rollers.

My understanding is that they claim reduced noise as the main plus.
Some of the claims in descriptions are clearly not true. Adjustments of their plastic bearings are not faster or more easy compared with any good roller based slider.

If you want something cheap, with exceptional quality - I suggest Varavon. They use only rollers. But they are very good.