I tend not to make product suggestions since there are so many variables involved in doing it right. But, there are some questions you should answer before anyone can make any meaningful suggestions.

Why do you want to buy a power amp? The amplifiers in the HK receiver should be capable of driving the Polks to satisfactory levels. No? If the power amps in the HK are not getting your speakers loud enough, you probably need to consider changing speakers before you spend your money on an amplifier. More efficient speakers will gain more volume dollar for dollar than a higher powered amplifier will achieve. This is especially important when you consider quality tube watts are not cheap.

If volume isn't what you're after, what is it you want from the system? What are your ideas on how the system should sound? What is important to you in reproducing music and what can you live without? Any system, and most particularly any system built on a specified budget, has to take into account the compromises the listener can live with. What does the present system do to meet these goals? Where does it fail? Why do you think a power amp will resolve the issues when you are still dealing with the same source components and speakers?

In explaining what your goals are for the system, please refrain from merely stating the obvious. We all want a clear midrange and open, airy highs wih a "good" bottom end. Anyone who has been around audio for a while knows those qualities are first of all personal and what pleases one person might drive another from the room. Also, getting those qualities is often a very expensive venture.

I find it most helpful if you try to put your system goals in terms that relate to what you are hearing at a live performance and then not hearing at home. What doesn't your system do for you when you get home from the concert? Why would a power amp resolve the issue?

Finally, how will you buy this amplifier? Will you have an opportunity to audition several amps before making a purchase? Which amplifiers can you audition? Or, are you going to buy what someone suggests without listening beforehand?

If you end up looking for power amps don't forget the 200W RMS @8 Ohms mono Le Amp II for $300.