Id reccomend deal extreme , They are very cheap , the players will definatly not be hacked , and the support is very good , Although they do not spe******e in MP3/MP4 players they have a wider range thzn uxcell.
Personally id reccomend buying a
http://dealextreme.com/details.dx/sku.5657
Its rockchip so it can play video and do other stuff at the same time(multi task) it has 1gb of internal memory and a ncie high quality machine , if you buy a 2gb sd card with it that is 3gb (almost meets your 4gb requirments.
If you want a highyer quality player go for the MEIZU M6 , but not yet ... because a new (updated) version is coming out shortly .... there is infact 2 new versions , the SL which is only 7MM thin (thinner than the ipod nano) and also the SE which i presume is also only 7MM thick but it dosnt require the video to be converted before you put it onto its 8GBs of internal memory
it has a much fatser processor , all of the players ive mentioned are in the $200 price range and the M6 4GB is only $89.99