Hola, Yes the price of cars does vary around Europe because of different taxation levels. I was speaking to a Dutch neighbour and in Holland there is a 24% tax as a car is seen as a luxury item! OK - sources of new car price info - obviously the net ie Nissan have a great site where you can select the model, options etc and they give you an online quote! There is also a little (ie half A4 size) magazine published which lists all the prices - I cant remember its name exactly (and I have just thrown out all of car mags as I have just bought a new car) but you will see it in magazine shops/kiosks.
On my car with a bottom line price of 25,000 euros - IVA (vat) was 16%, Costs of registering the car and getting the registration etc was 7%.
I got a better deal by selling the old car privately and buying new for cash without trade in. Discounts depend on the model etc ie usually on brand new models there is no discount.
Car sales have slowed a bit so you might get a deal! Remember you need an NIE to buy a car as it is a taxable item. Good luck.