I don't know about the Astrale series, but Cateye's Strada series is quite popular.
Cateye Strada Cadence RD200
has the features you want...plus some. It's not wireless, though; you'd run the wire from the chainstay to the handlebar. You can find these for ~$40.
A wireless version of the above, [url=http://www.cateye.com/en/product_detail/552]Strada Double Wireless RD400DW, doubles the price: $75-100
If you can live without the cadence feature, you can get the Strada Wireless RD300 for $40-60 or the wired RD100 Strada for even less. I've been using RD300s for the last 20,000 miles. Easy to program, excellent water resistance, good battery life, readily available replacement parts if needed. No issues other than an underground sensor at one intersection that momentarily trips the speed to 60mph, but this isn't uncommon with wireless computers. Cadence might be nice initially, but isn't critical. If you count crank revolutions for 15 or 30 seconds occasionally initially, your legs will be quickly trained to tell you when you've dropped below your target cadence range.