When I was 16 I bought my first set of speakers, an actve 5.1 set for £20 including delivery. The sound was less than stellar.
I then bought a pair of wharfedale valdus 500's as I wanted the biggest speakers I could get, coupled to a tangent amp 50 (which is quite good for £50).
Then did a part exchange with a carlsbro keyboard amp i found in a dump (15inch woofer) for a wharfedale diamond sw 150 and handed over £20. I kinda broke the sub and the dust cap blew off and is now replaced with a mr Kipling red lid (sounds fine to be fair, can't tell the difference, neither could the salesman).
Upgraded the amp to an arcam alpha 9 for £155, however I'm likely going to sell it for a behringer a500 as my source is a soundblaster external card and the speakers are also a limiting factor in sound quality.
As to the future, ultimately looking to get a second hand set of b and w's/monitor audios when a great deal comes along and a dacmagic/inequivalent, will keep the wharfedales for house parties and going to build some cheapo speakers for rears in the basement rave house room from car components, power them with the epic tangent and hope it doesn't blow up
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And finally i wish to build dual 15inch/18 subs in a sealed cabinet and power it with a pro amp to really shake down the house. I want to keep this for a long time so I'm going to get some audiophile drivers for this one not pa/car audio rubbish (to be fair high end car audio is fine but I want deep bass so pa is out).
Now 19 and I have easily made the money back through djing and from my perspective buying those £20 speakers was one of the greatest purchases I have ever made. I heartily recommend you go down the route of separates for your children, it really is a life long gift. I don't think I'd ever be happy in life with a set of bose speakers now but before I learnt the difference I would have been delighted.