Just my
If I'm gonna spend $30k+ for a car... I'm not gonna look for parts for it on ebay...
That being said, if you're looking to change the tone, and gain some power then go for a full CBE and save for it. You'll be much happier in the end with the gains in both sound/power you get.
If you go the route you're talking now, yes the sound will be different and a lot raspier. However on the performance side of the house, anything you do to the front end to allow it to flow better you will negate with the stock system. If you put in test pipes you're still gonna have the same bottleneck in the Y pipe. If you replace the Y pipe you'll still have a bottleneck in the muffler. Either way all of the 'improved flow' you gained will still eventually get stopped and you'll lose performance at the expense of rasp. Not exactly what I think you're going for.
All in all there are several different CBE's out there to choose from, and each have their pro's/con's and are in a wide expense bracket. Surely one from a good name at a slightly higher premium will give you what you're looking for without any negative side effect.