For various reasons that I won't go into here, I am gradually shifting my testing from Kprobe to CDSpeed Disc Quality Test. I am noticing a lot of others here in the forums are making the same switch.
I primarily test with a Liteon 1213S flashed to 1633S, presently using the BYX2 Sony firmware. It rips very quickly, does a good job of running quality scans, and even writes very nicely at 8x on JPNR01 and PRODISCR03 media.
Another good candidate would be the Benq 1620. Excellent writing quality on +R media, and also writes very well on high-quality -R media. Seems to be a good scanner using CDSpeed, and the results at 8x are almost as good as at 4x, which will save you some time.