lots of good advice in this thread already,but i think i'll give it a go and hope i don't wind up with my foot in my mouth,so here goes.....when you compare your stuff to bigtime commercial stuff you hear on the radio,you are usually hearing a mega-buck mastering job as well as the mix.that factor,in my humble opinion,is a major player in the consistency of the bigtime product as compared to ours.....so here are a couple of sugesstions from a guy who has spent some sleepless nights reading all i can find about mastering and trying to apply it.first off,get some up to date monitors.i know those old jbl's are as comfortable as an old shoe,and i bet your mixes rock on stereo speakers of the same era.but the guys that are designing reference monitors are designing them based on mainstream consumer gear that is prevelant today(cd boomboxes,bookshelf systems etc.)...don't be afraid of some radical panning,this can give the instruments their own space in the mix,along with some width enhancement at the mastering stage.i use cool edit pro and soundforge,both of which have some cool enhancement.....check often in mono though,to make sure it isn't collapsing on you.cheap boomboxes and such don't always boast the best stereo separation specs,so they can use all the help they can get.someone mentioned cutting at 250 hz,which clears out low,mid mud,try a cut at 150-160 of about 2-3 db also...my final step is usually to normalize to rms(average loudness)in soundforge usin the equal loudness contour(fletcher-munson curve)to an average loudness for the song of about -12 to -14 db,depending on the type of music i am doing.i have spent a lot of time loading commercial cd stuff into cool edit and loading up the statistics and looking at them and looking at the freq. rseponse on the cool real-time anylizer and trying to copy it.my stuff still doesn,t sound as mega-buck as the big guys,but i'm getting a little closer every day.hope i've been able to help....good luck