SQL 2012 :: Case When Statement With Dates

SELECT
SUM(((CASE WHEN
o.date>= a.activity_date, other filter condition, other filter condition
THEN
(select coalesce(d.balance,d2.balance) from drawtable d where coalesce(d.date, d2.date) < a.activity_date order by d.date desc limit 1) - ( select coalesce(d.balance, d2.balance) from drawtable d where coalesce(d.date, d2.date) = interval 'current date'
else end ))

from
emailtable a
LEFT JOIN opportunity o
left join drawtable d
left join drawtable d2
etc

The tricky part is I'm joining that same table twice.....would this be better in a max/min case when statement?