I personally love Happy Valley. Of course it is not as "happening" as Midlevels or other areas, but you will find what you need and it's so close to Causeway Bay/Wanchai anyway. Extremely quiet (in terms of traffic noise) in the morning and evening/night, even along the main road. Lot's of green as you see the mountains from nearly everywhere.
Not sure about your budget. I gave my agents a max of 15K, and also asked for older apartments. Unfortunately the old ones turned out to be really old and not cleanable (revamp would be necessary, often with ugly built in furniture you can not remove). Some with nice roof terrace.
In the end I decided for a smaller, but nicer place.
Sure you will find something great in the 2-3br category if you pay a bit more. If you want to get a feel of it, just ask some of the property agents near the tram stop to show you around. There are plenty to choose from.
Very happy in Happy Valley