Any day, having a power amplifier is totally different from having AV receiver alone. Having said that, you need to see if you really require a power amplifier. Also, you need to see if it is worth to make an investment. If you are satisfied with those criteria, then you can really go for a seperate amp.
I came across the guide lines (given below in the quote) on THX certification which is all about the ability of AV receivers/amps to drive the speakers (with minimal distortion) in rooms of varying sizes. Here is a quote from hometheater.com and that gives you a rough guide line on using AV receiver -vs- seperate Amplifier.
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The AVR is stereotyped as the puny kid backed up against the wall by brawny separates who grab his lunch money. Nonetheless, an A/V receiver is usually the best way to fill a small to medium-sized room with surround sound.
Whats small to medium-sized? One rule of thumb comes from THX certification: THX Select2 Plus AVR-based systems are certified to produce cinema reference (high) sound pressure levels in rooms of up to 2,000 cubic feet. Lets call that a small room. THX Ultra2 Plus systems are certified to do the same in rooms of up to 3,000 cubic feet. Lets call that a midsized room and anything larger than 3,000 cubic feet a large room.
But room size isnt the only considerationor even the most significant one. What matters more is how your A/V receiver mates with your speakers. Speakers with nominal impedances of 8 ohms are easier to drive than those rated at, say, 4 ohms. Another crucial factor is sensitivity, or how much volume is produced per watt of power, specified in decibels under specific conditions. Speakers of the highest sensitivity (into the 90s) and moderate impedance are an easy load even for a modestly powered AVR operating in a large living room.
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So check for your room size and the connected speakers spec. As sandeepmohan suggested, if you have very good speakers (with high sensitivity and higher impedance) and room is mid-sized, then SR7005 itself can drive your speakers with ease.