you can use what you have.
you can use both peices of gear that you now have & use other (bolt on) processors,dvd player & speakers at a minimul cost.
here is a link to an add on processor from ebay that will allow you surround sound & still be able to use your pre & power amp,with this peice half the equasion is solved at little cost.
http://cgi.ebay.com/NEW-IN-BOX-Kenwood-SS-592-AV-Surround-Sound-Processor_W0QQitemZ260013470937QQihZ016QQcategoryZ14978QQrdZ1QQcmdZViewItem
Or............ at even less cost you can simply buy a NILES AUDIO speaker selector that will allow you to use multiple sets of speakers from a single power amp,the trick to this approach is to get a speaker selector that has independant volume control for each channel & that is able to use different impendance speakers so you are not forced into a certian ohmage speaker for both pairs.
im going do differ with the other posts in reccomending that you invest the bulk of your budget in a GOOD pair of full range main speakers that can dig down to 20hz or as close to that as possible,for me a good dynamic sound with high impact is the most important thing in watching movies,sub's are not needed if your mains are able to give up the bass & you are not using an internal xover inside the preamp which your crown dont have anyway.
If i was in your budget range with the nice gear you have allready i'd do this.
1 use the crown preamp.............zero cost
2 use the hafler amp to power all speakers because its a great amp with plenty of power........................zero cost
3 buy this niles speaker selector...........very little cost.......
http://cgi.ebay.com/NILES-SVL-4-SPEAKER-SELECTION-VOLUME-CONTROL-SYSTEM_W0QQitemZ270012241733QQihZ017QQcategoryZ64596QQrdZ1QQcmdZViewItem
4 Look for clean used speakers from cerwin vega or NHT,like these for your mains.
http://cgi.ebay.com/Cerwin-Vega-Cerwin-Vega-AT-15-Speakers-Vintage-Like-New_W0QQitemZ130010931306QQihZ003QQcategoryZ71569QQrdZ1QQcmdZViewItem
5 The same brand used for your mains should be used for the rears if possible as its easier to voice match the speakers,like these for rears.
http://cgi.ebay.com/BNIB-CERWIN-VEGA-PAIR-VE-8F-FLOOR-SPEAKERS-300W-NR_W0QQitemZ330012106666QQihZ014QQcategoryZ71569QQrdZ1QQcmdZViewItem
6 You can add a center channel by using another speaker out tap on the niles speaker selector & achieve a blended l&r center signal ,here is a decent model.
http://cgi.ebay.com/Cerwin-Vega-Center-Channel-Speaker-Used_W0QQitemZ150014418244QQihZ005QQcategoryZ14992QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
by running your gear in this fashion you will not have true surround sound but you will have a great sounding system that is highly dynamic for watching movies,for me the dynamics of the sound are the most important thing in watching movies ,wit the niles unit you can adjust the different speakers volume levels so the rears & center give a well blended mix , i can live without the sound of a stray bullet whizzing from behing my head,there is very little sound that really comes from rear & side speakers in a true surrround system.
i have my big rig set up in this same fashion & i much prefer the way it sounds over the previous versions i had when i was running 5.1,the gear you have now plus the gear i listed in the links will blow away any $1,000 htib system that you get at best buy.
just some suggestions.