No telescope that fits your budget and observing habits is overkill.
As you may have read, the bigger the aperture, the more light it collects, and the finer detail it can resolve in steady air.
A 5-inch f/5 reflector (650mm focal length) is good for wide-field views of deep-sky objects and easy to transport to a dark site.
It should show the rings of Saturn clearly with a 10mm eyepiece (65x magnification); a shorter eyepiece could double that without losing clarity.
However, with such a short optical tube assembly, you might either operate mostly on your knees or put the mount on something less sturdy than the ground.
Also if the secondary mirror is exposed as shown here, it's vulnerable to dew, and stray light can enter the eyepiece and reduce contrast.
If you're primarily interested in planets, a 6-inch f/8 reflector (1200mm focal length) could be an even better choice.
A 10mm eyepiece gives 120x magnification, the primary mirror is less sensitive to collimation error, and the secondary mirror can be smaller for slightly better contrast.
On the other hand, you might want an additional eyepiece longer than 25mm for better views of certain faint objects.