Can anyone make this sql query faster

Hi Guys,

we've got an old sql query that powers the 'Manage Customers' page thats slow as a dog to run. if anyone has a few minutes to review and rewrite this query so it run faster it would be greatly appreciated.

theres the sql

SELECT
    c.id AS CID,
    c.name AS name,
    (
		SELECT (CASE  WHEN c.enabled = 0 THEN 'Disabled' ELSE 'Enabled' END )
	) AS enabled,
    (
        SELECT
            coalesce(sum(ii.total),  0) AS total
        FROM
            si_invoice_items ii INNER JOIN
            si_invoices iv ON (iv.id = ii.invoice_id)
        WHERE
        iv.customer_id  = CID 
	) AS customer_total,
    (
        SELECT
            coalesce(sum(ap.ac_amount), 0) AS amount
        FROM
            si_payment ap INNER JOIN
            si_invoices iv ON (iv.id = ap.ac_inv_id)
        WHERE
            iv.customer_id = CID
	) AS paid,
    ( 
		SELECT customer_total - paid 
	) AS owing
FROM
    si_customers c
WHERE 
	c.domain_id = '1'
ORDER BY
    name ASC;

just post your improve query in the Simple Invoices forum:
- http://simpleinvoices.org/forum/discussion/864/can-anyone-make-this-sql-query-faster/

Cheers

Justin