After debating the upgrade for almost a year, I finally decided to give it a try. I replaced the pre-amps two NE5534A op-amp chips with a pair of Burson Supreme op-amps. From pulling my pre-amp from the rack to listening to music again took less than an hour. I was delighted when I turned it on and it worked without a hitch. The Burson Supreme op-amp has added tons of low end and has a nice smooth tone across the entire frequency range.
I defy anyone to find an upgrade this effective for this good a value.
Thanks again Burson, totally worth it.