Dunno about P5B-PLUS. Agreed about Striker and P5N32-E SLI, there's no useful difference IMO. Actually, the P5N32-E SLI comes in 680i flavor (most similar to Striker) and 650i flavor (better for overclocking, apparently).
If we're talking about top-notch components and a nice budget you should take a look at the Gigabyte GA-N680SLI-DQ6. It's a bit more expensive than the Striker but it's worth it. I was planning to get a Striker but apparently Asus mobos are not that good this year.