If you are satisfied with Cultus then no need, Cultus is a good car as well but if you need money then that is another story.
Comparing it with LIANA, Cultus has no match for a Saloon car. I usually drive/sit over a new Cultus (June 2015), but the drive pleasure and feel of my LIANA 2008 is still much better than that. Whether you are driving it or traveling in it.
As you have bought the Cultus new, and have maintained it since then, your Cultus might be a trouble free car for you. And buying a used LIANA can be a trouble some affair, if you do not choose wisely for the car.
VURV tag is nothing, just a marketing gimmick with a software update, the car is all similar. If you can find a good LXi, it will be good.
My opinion: If you are satisfied with your Cultus, do not opt for it.
If you are looking for a more comfortable ride, go for it. But it won't save you that much money in the exchange.