I did some online research on this a while back and the ones in my price range (anywhere under $300) that consistantly got good reviews were some $225-275 models from whirlpool - mine is a whirlpool whispure 510. I also saw these at sears a couple weeks ago under the Kenmore brand name.
They are about the size of a normal $10 box fan - 2 feet tall x 19" wide x 5" deep, give or take a bit.
I bought mine online from abtelectronics.com and overall it was a very positive experience - well packed, showed up before I expected it, price was cheap compared to others, etc.
As for the filter itself - after I got a golden retriver, I put the filter in my bedroom and leave it on overnight and occasionally during the day. The air definitely smells "cleaner" in there.
On the low speed setting the filter doesn't make too much noise. Anything other than that, and you can definitely hear it.
Edit: Since you mentioned the ionic breezes, I was assuming price wasn't an object - for what it's worth, when I was researching I started in the $50-$100 range, but the overwhelming sentiment seemed to be that those didn't really do much good. These $250 whirlpool whispure models were the ones that were being recommended for people with real allergy problems etc, who couldn't afford the "good" $1000 air filters.
Edit2: Some more stuff, while I'm thinking about it - this unit has 2 seperate "filters" and has little lights to indicate when (time based) you should replace each. My light just turned red for the "prefilter" which is a cheap ($10-15?) thin filter that lays on top of the real hepa (I think like $50?) filter that does the real filtering... My hepa filter light is at the 1/4 used mark, so at this rate I figure the normal filters will last at least 4-5 months and the hepa should last 14-18 months or more.