i wouldnt say that your non sub system didnt get much praise.. i think some people also forget that some people dont have money to spend on a certain system, or that they just want something simple that is nice & clear & does the job.
good cheap 6x9s to get are the blue poly cone 3ways from super cheap which sell for about $70. they are excellent quality for the money. i ran them off the head unit in my celica and they did a fantastic job.
if you want to run splits, you should run them off an amp, so this will make this an out of the question option. just get some good 3 ways for the front as well, i find that kenwood 3 ways are excellent, get something around 130 or 150w.
then get a decent head unit, something like an entry level jvc or kenwood unit with at least 4x45w. you can pick these up for about $280-350
6x9's will provide plenty of bass for you for the time being, forget about all this sub bass hype, mid bass will satisfy the majority of people, and then when you can afford it, later on you can add a sub & an amp. grab one of those cheap sony 222w or 444w amps, and a 10" or 12" sub for around the $180 mark in a premade box. there will be a little extra installation for you, but in the end it will all be worth it.
i used to have a 4x45w head unit, 130w pioneer 2ways and 140w kenwood 3ways just running off the head unit. and that did a fantastic job for me for around a year. it was only when a mate sold me his kenwood amp that i ended up buying another amp & a sub. until then, that simple setup worked a treat.
in my celica, i had a 4x30w head unit, cheap no name brand 3 ways in the front, and the 6x9s in the back. i probably should of upgraded the head unit, but seriously, it all did the job quite well and the 6x9s served their purpose well.
otherwise, you suggestion above with the 4 channel amp, sub, and rears off the head is a good option to go, but you'd be looking at spending a fair ammount of cash. but its a very good idea. as i suggested before, check out large chain stores for their discount offers, or check out the local cash converters or other 2nd hand store that buys the old stock of the chain stores, so its brand new, never used & half the price, and you get the option of layby too.
for bang for you buck, get all jaycar equipment. you can get everything you need from them except the head unit & all for a decent price. and its good quality gear too.