Those SP-BS21 are currently $62 shipped.
They often come on sale for $49 shipped.
The slightly larger SP-BS41
's will have a greater bass extension. They are currently on sale for $99 shipped.
They are simply untouchable for the price.
I bought a pair of the SP-BS21's for a friend. Hooked them up to my dayton 15 wpc class T amp and was blown away by the sound.
Very smooth, lifelike vocals. Detailed highs without being harsh, and respectable bass output. I'm sure the SP-BS41's will have even more bass.
Don't think that pioneer designed these in five minutes to mass produce them and sell them on their name alone. Andrew Jones, a well known expert designed these from the ground up to bring to market the best speaker possible in that price range.
Here is another amp option
. Similar to the amp you linked to earlier, just with a much smaller footprint and the added benefit of an integrated headphone amp.