mp3sparks is the latest venture of the "entrepreneurs" from AllOfMP3.com. Their business is borderline legal in Russia, but, quite importantly:
your use of their business is illegal in Russia and in the US. The only thing protecting you right now is that their transactions are shielded by their borderline legality. If that shield breaks, get ready for RIAA lawsuits like you've never seen before (and with a whole lot more convincing evidence - your credit card authorization - than in any RIAA lawsuits to date).
Note that of course their web site FAQ says differently (although not in very strong language ... something like "we think it's legal to use our service in the US because of fair use exceptions"), but they also expressly disavow any knowledge of laws regarding the use of their product inside or outside of Russia.
More importantly, though, it's highly immoral. No one who produced the music gets any money from this. Who gets the money? After network and equipment fees, it's 100% profit for the guys running this. Some would assert that this money goes to the Russian Mob, and that may be true or not. All that's important to me is that it does
not go to anyone remotely involved with making the music. As such, paying them is no better than downloading from a torrent or Kazaa (are they still around?). I'd rather 2 cents of my dollar go to the artist than nothing, frankly. They still get screwed, but at least they can buy beer to drown their sorrows

And, if I'm going to deprive them of
any money, I don't see any reason to pay some unrelated third party for the privilege.