few suggestions,
first there is no way you can buy Dyns for $400 - $600, retail is $1099 for the system 242
I would also suggest that 2nd hand is always an option. you can generally get better gear for less, so long as you are willing to purchase without a warranty.
I would also suggest to most people to build their own sub box, costs so much less than paying someone to build one or buying a prefab one, it is dead easy plus prefab boxes arent suited to every sub.
and one final option I would probably suggest to people would be if they only have a certain budget now then to perhaps buy in stages to build up to a better system. if you buy crap now you are just going to end up replacing it in the future anyway. for example, if for now I only had $1000 to spend, I wouldnt bother with a sub or amps for now. I would prefer to buy a decent HU say $300-400 plus a nice set of splits $400-500. then I would save up some more then buy a speaker amp to power the splits. save some more and buy a sub and mono. i know a lot of people want it all now but it will be so much more worth it in the long run if you take your time. (please note that this is just what i would do and understand some people just cant afford to keep saving and spending more on audio, for me I am never finished, I just bought and installed some new amps this week, just for a change)