Any 4 or 8 ohm speaker will work with your 2215B. If you can, try and audition any speakers you are interested in buying using a similar amplifier of moderate power, i.e, about 20 watts.
Specifications can't tell you very much about how a speaker will sound in your room, with your system. If buying new, make sure you have the right to exchange the speakers within 30 days for store credit or refund for a different model of speaker.
If buying a pair of vintage speakers per the earlier post, if you find you don't like them you can sell them for what you paid (if you do your homework and don't pay too much), all you might have to eat is the shipping cost.
If you are on a modest budget, there is no way any new speaker costing less than $500/pr is going to outperform the vintage speakers noted previously.
Fifty percent of the cost of manufacturing a loudspeaker is the cost of the cabinet. After engineering, manufacturing, marketing, and shipping, only 20% of the total cost is for the drivers. These vintage speakers all have very solid well made cabinets, the kind that cost several hundred of dollars each to manufacture today, yet they are undervalued in the market. They are not the largest, loudest, or rockingest designs but they do a better job of reproducing the sound of musical instruments and human voice than much of what passes for audio loudspeakers today.
Don't be afraid of buying a speaker like the Smaller Advent that needs to have the woofer surround replaced. This costs about $30 per speaker if you send out the driver. If you do it yourself, it costs only about $20-25 for enough surrounds and glue to refoam one pair. If you don't want to mess with repairing the woofers, there is a pair on eBay now that are available with newly refoamed woofers. The starting price is $65 and the Buy-It-Now price is $100.http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3088071519