PENG said:
hifi, I think that is only a concern for receiver and entry level amp owners. Mid to hi end power amps that are designed to drive 4 ohm (nominal) loads should be able to deal with the dips to 2 ohms or lower, and hard to drive (e.g. highly inductive) speakers
I agree but if he had said his budget was like $500 or something his choices would be severely limited to mostly pro amps & if his speakers impendance dropped to 2 ohms or lower then the choices would be even smaller so i wanted to clear all that up right from the start.
Nordhaven,i can think of a few amps & i'll post the names but if i were you & i was looking for the most bang for the buck i'd hold out for a pair of CARVER SILVER 9 T MONOBLOCKS,they put out 550 wpc @ 8 ohms,900 wpc @ 4 ohms & they are 2 ohm stable,these amps are work horses & have good looks plus their resale value will only go up in price,if you ever decide to sell them you cant loose money.Being that the silver 9's put out 900 wpc & you only need 400 to 600 wpc the amps will always be loafing & you'd have enormous amounts of headroom.
Expect to pay around $1,500 for the silver 9 t's if they are mint with the smoked glass bases.
http://cgi.ebay.com/CARVER-Silver-9-t-Monoblock-Power-Amplifiers_W0QQitemZ260081311603QQihZ016QQcategoryZ67786QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Another good amp that fits your requirements is the MCINTOSH MC 7200,the mc 7200 is a non autoformer amp(direct coupled) & will double down in power with lower ohmages,the amp is rated at 200 wpc @ 8 ohms & 400 wpc @ 4 ohms,this amp has a great feature called power gaurd which is a soft clip feature that works by sensing if the distortion level ever rises above 0.005%,once the sensor detects distortion it lowers the volume just enough to keep the distortion below 0.005% & automatically turns the power back up once the distortion has passed,all this is done without the listener ever hearing a difference in spl's or sound quality,this amp is also another no loose peice of gear that retains abnormally high resale value.
Expect to pay between $1,200 & $1,500 for a mc7200 if its mint with all packing materials.
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1173624001
A favorite amp of mine is the ADCOM GFA 565 monoblocks,i own a pair of these amps with white faces & they are killer amps especially for what they are capable of,the amps are rated for 300 wpc @ 8 ohms & 450 wpc @ 4 ohms & they have a very high resale value.
Expect to pay between $900 to $1,200 for these depending on condition & packing materials.
http://cgi.ebay.com/Adcom-GFA-565-Mono-Block-Amplifiers-Excellent-Condition_W0QQitemZ140082029228QQihZ004QQcategoryZ71543QQrdZ1QQcmdZViewIte
Another amp that would meet your requirements is the CROWN MACRO REFERENCE PRO AMP, i just picked up one of these amps last week & im still testing it out,so far the amp performs excellent,im comparing it against my mcintosh mc 1201 1,200 watt monoblocks,the crown is rated at 450 wpc @ 8 ohms, 600 wpc @ 4 ohms & is 2 ohm stable.
Expect to pay between $1,200 & $2,000 for the crown,i paid $1,300 for the one i just bought.
http://cgi.ebay.com/Crown-Macro-Reference-The-Best-Crown-Amp-Ever_W0QQitemZ320079061569QQihZ011QQcategoryZ64451QQrdZ1QQcmdZViewItem