Mark:
I've been living on a well for about 3 years now and here's what I understand.
The size of your pump determines two things: 1) The
maximum pressure your system can achieve and 2) The maximum flow rate your system can achieve. A 1.5HP pump is probably about the minimum you would want - check the specifications for the pump.
The pressure tank has one main function - to keep your pump from turning on every time you turn on a faucet. This is highly desirable since the life of your pump is measured in on-off cycles not in hours of run-time. The size of the pressure tank determines how much water you can draw from a faucet before the pump will kick on. There are two settings on your pressure tank - the pump kick-on pressure and the kick-off pressure. When enough water is drawn out of the tank that the pressure in the tank drops to the kick-on level, the pump turns on and pumps water into the tank until the pressure in the tank reaches the kick off pressure.
The range between kick-on and kick-off is usually 20 - 30 PSI and it is usually set something like 35PSI on and 60PSI off. So, when you stand in your shower, you will find that the pressure gradually drops - then builds up - then drops, etc. This is the pressure drawing down, the pump kicking on, building up the pressure, kicking off, etc. The objective is to make this cycle last around two minutes at least (with the shower running) - so as to reduce the number of pump cycles and extend its life.
You can adjust the pressure controller on your pressure tank. There is a high-limit (kick-off) setting and a low-limit (kick-on) setting. The adjustment is very sensitive. Once you set it, you must adjust the air pressure in the tank to be 2PSI more than the low-limit.
If you set the high-limit above the maximum pressure that your well pump can generate when a faucet is on, your pump will kick on but not kick off until you turn off the faucet. I have been told this and it makes sense, but I have not done it. This would be very useful if you water your grass or garden for long periods - you could get max pressure at your hose and not use up any of the pump-cycle life.
I suppose a second pressure tank might help but it would be difficult to figure out the plumbing/pressure settings. A BIGGER pressure tank would certainly help by storing more water and lengthening the cycle time.
Regarding your whole house filter: This will limit the maximum flow (and percieved pressure) from your faucets. Read this information from the filter cartridge label. If it is just a rust/sediment filter it's probably around 5GPM. A carbon charcoal filter will be much less. Also, the flow rate will decrease as the filter clogs up.
I installed two whole house filters in parallel. This increased both the initial flow rate and the length of time before I had to change the filters.
I suspect that your dissatisfaction with the pressure at your tap has more to do with your filter than with the pump or pressure tank.
Go to
http://www.plbg.com. It is a discussion forum for plumbing. I'm sure you'll find a thread on this issue or someone to answer your specific questions.