i have a pair of the Rokit 8's and I like them quite a lot
bring some disc that you really like and listen to all 3 of those, and see which one you like the best. Maybe even see if you can borrow them for a day and have a listen to them at your studio.

-gil

I use Wharfedale 9.2 passives...only $500 and really solid. You would still need to add the price of a decent amplifier (more than 100W per side). I have also heard great things about Dynaudios, but will have to agree with Gil's suggestion of trying them out. Some dealers will let you try out monitors at your home if you let them hold some of your money. He's also correct that it is more of a matter of finding some where the mixes that sound "correct" to you also sound correct on the monitors you wish to purchase.

As far as mastering goes, there usually will not be any actual mastering going on in the typical small home studio. It should always be done with an unbiased set of ears in a near-perfect and purpose-built environment, with professional monitoring (not affordable). If this isn't possible, it should at the VERY LEAST be done on a secondary set of monitors (other than those you mixed on). Again, this should be done somewhere else, and by someone else.

My $0.02 (USD)

why for the ground does exploding?

Making the fun by foreigners is not for the nice!