Yes, I'd try to get in hikes with more elevation change than 700 feet.
They are not so close to the North Bay, but here is a list of 'challenging' hikes from the East Bay Regional Park District:
http://www.ebparks.org/activities/hiking/other_challenging_hikes . Mt. Diablo is included on that list. Not much shade there, so summer hikes can be hot.
The aformentioned Mission Peak is good for training with ~2100 of elevation gain over 3.1 mi one way from the Stanford Ave staging area in Fremont, though it is very busy on weekends. Monument can be had from Fremont as well. Ed Levin charges $5 parking, but it far less crowded, so you may prefer that access point.
I like Pleasanton Ridge Regional Park for training. There is about 1300 feet of elevation difference from Sunol to the peaks and lot's of ups and downs if you want some interval type training and/or more elevation change. Plus there is lot's of room for longer distance hikes.
For something different and closer to the North Bay, you could do the SF Stairways hikes which are usually about 10 miles long with hills and stairs. There is one this Saturday (5/9) at ~9 mi with ~2,500 of climbing. See
http://stairwaywalks.blogspot.com/ .
I've done some good day hikes at Point Reyes. See
http://www.nps.gov/pore/planyourvisit/hiking_guide.htm to get an idea of the wide variety.
The SF Sierra Club does a number of hikes in the Bay Area. See
http://www.sierraclub.org/san-francisco-bay/activities-and-events-calendar. And there are several meet-up clubs too if you want even more.
