I believe most bookshelf models nowadays are shielded. If anyone is aware of bookshelfs made in the last five years that aren't shielded, please correct me.
Specifications, if accurately stated (which is really the important thing, isn't it?
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), can be an important part of helping narrow down your speaker wants and needs, but most definitely shouldn't be the only criteria your speaker decision is made. Two different speaker manufacturers can produce essentially the same size speaker, same configuration with the same specifications, yet still have very contrasting differences in their sonic signature. Because of this, most will want to hear first-hand their speaker options before committing long term. This is where being able to demo a speaker or some companies having 30-45 day satisfaction/money back guaranties is an important part of your decision making.
In addition to specifications and listening evaluations, aesthetics can play a role, also. Due to the smaller form factor of bookshelf speakers, many manufacturers are considering their integration with existing furnishings and their WAF, which was more of an afterthought years earlier.
With you're budget being approximately $500.00 for a pair of bookshelf speakers, you should be able to find quite a few that may suit all your needs. If you'd like specific recommendations, just say the magic word...
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-TD