Instant calculations in quotes & invoice templates

Just wondering why it is not already possible to do this (or is it?) and will it be an option in future?

I would like to be able to set my quoting & invoicing templates to always calculate instantly according to what my pre-defined prices for products are.
The same with the tax calculation.

Currently i select my products & service from the pop up window that displays all pre-created items and insert them one by one into the quote. I then have to enter the list price instead of it appearing and calculating instantly. With each item i have to add the price I want to charge regardless of what price I have specified when creating the product or service and this is a little self defeating. For the moment it's not a huge problem but when it comes to cloning a quote for the purpose of minor alterations and creating options, if I change a service by inserting another in its place - for example i may replace "1 face painter hourly rate" with a "2 face painter hourly rate" - then depending on how much of a rush i'm in it easily easily be that I forget to make the change to the actual list price being charged becasue it doesn't automatically update with the change. If instead the figures for each product or service were automatically updated in th elist price column it would save a lot of double checking to make sure nothing was missed.

The same with the tax part of it. If I clone a quote then make several changes to it, it is easy to forget to re-calculate the tax percentage (and I actually have done so a few times and then had to stick with the price quoted - for customer service sake and it cost me). Why can the tax just not calculate automatically at once when any change is made in the pricing above?
It kind of defeats the purpose of having a self calculating template when you have to double check that all calculations are done correctly. It can be done with Adobe PDF forms (i created my invoice template a while ago and it did just that) so i don't understand why it can't be done here.

Can we at least have the option of choosing one way or the other when it comes to these things?

So to clarify I guess what i'm trying to say is
1. that variations on list price should be able to be done by editing whatever figure is inserted automatically when you insert the service or product being charged for (minimizing room for error becasue the only time you will change the list price is if you want to and how often do you need to anyhow?). I think the price books option offers some kind of control for that option if people want to utilize it but for those who don't need it there is no option (if i understand that correctly).

2. Tax should not have to be calculated then re-calculated anytime a change is made. It leaves too much room for error which can be costly. If this is useful to anyone then it should be a setting that is optional.

Hope you can change this soon as its very annoying. I think i have read other similar discussions to this on this forum so I figure its not just me.

Thanks for an affordable CRM otherwise.