Would you rather have old Hafler XL-600, (300 watts) or a new emotiva (250 watts) for about the same price. Both are two channel. I have rather fond memories of the old haflers from college. But don't know if the technology has changed for the better to be better served with a new amp. I know the old ones can be a little more troublesome, but hey so can the new ones sometimes!
Those old Hafler amps were great. That there are so many around now in the used market is a testament to their original design and build quality. Depending on the price you can get a great deal. I'm not sure if roughly $700 would be a good price for an XL-600. Check around on fleabay, craiglist, or audiogon to see prices.
As someone else said above, there has not been anything new in class A/B amp design in some time. The only thing new is cheaper ways to build them in China.
For repairs of old Haflers, there are several companies that offer mods or rebuilds on old Haflers - just search on "Hafler rebuild". One very good one that I know of is
this one by AVA, where they gut the original electronics while keeping the chassis, transformer and heat sinks. Its not cheap, but it would give you essentially a brand new amp of the very highest performance.