Speaker questions for 2007 Prius 2

I've got a 2007 pkg 2 with non-JBL audio. I had some speakers called Image Dynamics, some two-ways, installed in the front, but they seem to have completely come apart and were rattling like crazy.

Today, my friend and I installed this head unit, and these speakers:

Alpine CDE-136BT CD receiver at Crutchfield.com

Sony Xplōd™ XS-GT1627A 6-1/2" 2-way car speakers at Crutchfield.com

The head unit is great...we installed it stealth-style, with steering wheel controls. Surprisingly easy! However, the speakers are obviously average. We've left the stock tweeters in, as well. The Crutchfield advisor seemed to perhaps have steered me wrong, saying that these Sonys were the only ones that would fit! Weird. Anyway, seems like there's lots of options out there of stuff that does. So, here's my questions. Would love any advice from you experts here:

1) What would be a nice upgrade to the front speakers I just put in? Preferably something that Crutchfield stocks, so I can do an exchange. My budget is up to $150 for a pair. I'd like to not purchase an amp, and simply use the head unit's power. So, something that fits, that sounds great, and that is efficient.

2) Can someone recommend a reasonably priced powered sub (on Crutchfield preferably) that would be small-ish and relatively easy to install along with my system?

Thanks so very much in advance!
Justin

 

Just to clarify, regarding the sub:

I'd like something small and complementary to the system, perhaps one that installs in the cargo tray or under the driver or passenger seat. Perhaps this?

Sound Ordnance™ B-8PT 120-watt compact powered subwoofer at Crutchfield.com