There are good speakers that are cheap and bad ones. They'll sound the way they sound. Buying new electronics won't give you what you want. Good speakers will sound good, even when connected to OK electronics. Bad speakers will sound bad on the best electronics and there's nothing you can do to change this fact. You can EQ the crap out of the system and all that will happen is the speakers will meet their end sooner than you expected.
Sell the new speakers, learn from the experience and buy the best speakers you can afford. Build some from a kit if you can, or look around here for recommendations. They don't need to be big, or expensive but they do need to be designed correctly in order to sound good.
Another thing that absolutely needs to be remembered- everyone's hearing is somewhat different and that's why so many different speaker brands exist. Some similarities will exist between them but there can also be a vast difference in sound. A friend of mine tested a pair of Denmark speakers, which were owned by someone he works with. Bass was OK, highs were OK but the midrange was basically absent. The problem with this is that human hearing is most sensitive in the range that wasn't there. That's where most of the sound we need to hear lives and if it's going to sound real, it has to be reproduced accurately. Any woofer can be put into a box but there's no guarantee that it will sound good. All speakers have physical characteristics that dictate what box will work for bass response and bypassing this guarantees one thing- it's going to sound bad unless the person who built them either tried a lot of different ones or they just got lucky. In the absence of skill and knowledge, luck will do as long as the results are good.
