True, the cheap airport express model I had linked is indeed limited to only 54Mbps wifi, but you only going to need about 1 or 2 Mpbs for audio streaming anyways. Why get ferrari for getting groceries?
Is it legacy product without ongoing support? True, but there is no evidence that it won't work out of the box and price (for me $10 throwaway is not big deal)
You could always opt for x10 the price,
latest Apple's AirPort express model - which is much faster, supports all bells and whistles and possibly waste of money, but hey - it's not legacy
Win7 support?? Sorry - Not following you here. The OP's goal to stream from iPad/iphone using Apple's own Airplay . Last i checked Airplay is not native to windows. I can only guess you refer Apple configuration software won't work on newer windows versions?? I guess if OP has Mac at home - it shouldn't be an issue.
AppleTV is great device and a solid candidate for AirPlay receiver, However not only it's lacking analog port - it's also lacking any other port other than HDMI and given audio only centric system running on Integ Amp - makes it wrong choice.