There's a mass of telescopes, all with slightly different purposes.
For planets you need:
* Focal length primarily - you're talking 2 meters+ unless it's the moon. This is effectively the zoom. However the more you zoom the less light there is soo..
* light gathering (aperture) - the more aperture the more light can be brought to your eye. Aperature also defines the resolution of the image you see.
This is why you see telescopes that are for planets as large stubby/wide mirror reflectors or long large wide refractors (ie without mirrors). A 910mm focal length but 80mm aperture telescope will see something but you will find it very dim and low detail - so don't bother. The more focal length, the steadier the scope needs be or the planet will be all over the shop too.
For this reason, and your budget, I would strongly recommend a dobsonian. It's simple, manual and provides the best light gathering for the cost. It can do planets (although you may find you have to track them a bit as they move).
If you can stretch (with space for it) to an 8"/200mm dobsonian then you're going to get some very good views.
As footman has said - rather valley and first light optics are some of the best specialists and will help you.
Also you can, if you have the aperature, change the eyepiece and get a wide field for looking at nebulae etc.
I have a Pentax 105SDP with a mass of equipment. Focal length of 640mm but can just about do some visual on Saturn etc but it's not designed for visual use but for photography. If I had a second scope - then I would be very tempted with a dobsonian. The views through a 16" were superb but what really blew me away one year was the view through a 24" (read $$$) dob but the largest apertures like this then suffer if there's light pollution.
