Forget about that system you picked out at Walmart.
X2
Are you looking at just putting the low end everything in? Pioneer isn't the name is once was. The low end stuff should be left alone from them now.
If you want a decent deck at low cost...I'd go with a Kenwood or JVC. Mainly because they have a lot of EQ abilities and generally have a lot of features for the lower end models. No so true with Pioneer.
If you want cheap quality sounding speakers...can't go wrong with Infinity. Cheap, easy to find, and sound amazing for the price.
You've kinda shook the hornet's nest bud.
I would expect a lot of debating and a variety of opinions.
The 2 main different kinds of advice you'll get will be...
1- Professional opinions. Those of us who are MECP certified and do this kind of work on a daily basis as a Profession.
2 - Backyard mechanics who have done this kind of stuff at most a few times with personal vehicles. But usually base their information off one single event.
Now, I'm not trying to be insulting to anyone. Just make sure you're getting correct information. Just because somebody says "I have these in my truck and they are the BEST". Doesn't mean they are...everyone has different tastes. Some of the backyard guys wouldn't even notice a sound quality difference that Professionals hear a mile away.
Some professionals don't have experience with as many brands as others. That makes their opinion kind of biased.
Good luck