Front speakers are not a problem, I got 6.5in components in with the use of some mdf spacers. There isn't really much need to replace the standard wire unless you are a complete audiophile, it generally becomes more important when wiring up subs.
There are far better speakers out there for the money than Blaupunkt, not saying they're not any good, but just not the best.
Make sure you go for components, and consider Rainbow, DLS, Genesis and MB Quart.