Show (base + attribute) prices in dropdown + "Starting at"

Selling goods with a base price, plus an attribute (size) dependent cost:

Base price: 10.00
XS: + 5.00
S: +7.00
M: +9.00
XL: +12.00

or put differently:
no base price
XS: + 15.00
S: +17.00
M: +19.00
XL: +22.00

I'd like to show:

(i) "Starting at" [price] in the listings
(ii) The total prices in the attributes dropdown menu

• there seem to be a "Starting at" string, but not sure where it's used/turned on?
• any idea how the lowest price could be shown after "Starting at"?
• any idea how to get the total price in the dropdown or next to radio buttons?

Product is set to

Product Price: 0.00
Price by Attribute YES

Attributes are set as:
no prefix 15.00
no prefix 17.00
no prefix 19.00
etc.

Now the display price will be the lowest possible price of each of the Option Name Groups ...

This will combine together to make up the lowest price ...

Great, thanks for the quick reply. If I may follow up; are attribute prices like this always without tax?

And, is there any way (except hacking the code) to display "Starting at" in category/features/new listings?

Any input appreciated.

If tax is set on the Product ...

If Display prices with tax is on ...

If you are logged in with an address in the Tax zone ...

If you are a guest and the shop address is in the Tax zone ...

You should be seeing the Display Price as well as the Attribute Prices with tax ...