Well a cheap Alpine head unit would still make your stock speakers sound better than your stock head unit did. But without buying new speakers it will make only a pinch of difference. Aftermarket speakers are the way to go if you just want a little pump of bass but anything more just get a nice...
Well it would be better if you gave us a specific model of each sub to compare, cuz both companies make amazing subs, it just matters what kinda sub you choose from them,
But all in all to answer your question the best i can i would go with Rockford, all rockford's products are great not just...