Melinda, lots of posters on the Home Decorating forum have gone down the road of searching for the perfect white. Depending on how many responses you get here, you may want to repost over there or do a search of that forum with the words "white trim."

Here is a link that might be useful: Home Decorating forum

There are as many "perfect whites" as there are opinions about them. The bottom line is, what undertone do YOU want for your space. Do you want something warm or cool?

I've got a copy of House Beautiful Colors For Your Home. There's a section called, "Which white is the best white?" There are 9 whites featured based on designers' opinions. Here's a list of those whites plus popular ones on Garden Web:
Pratt & Lambert (P&L) Silver Lining 32-32
Mixture of Benjamin Moore Linen White 912 & Decorators White 04
Farrow & Ball Strong White 2001
BM Super White 02
BM Ivory White 925
Acadia White AC-41
Decorators White 04
Ralph Lauren Pocket Watch White WW11
P&L Seed Pearl 27-31
F&B All White 2005
Cloud White OC-130
White Dove OC-17
Simply White OC-117
Marscarpone AF-20
Mayonnaise 2152-70
Acadia White AC-41
Monterey White HC-27
Bone White 03

Get the paint chips first. Lay them on a pure white piece of paper. This should help see some of the undertones. Once you've narrowed down your choices, get sample paint. Paint some scrap wood or stiff poster board and lay it against the wall(s) to judge the color & light.

Good luck!

We did BM Decorator's White for our trim and kitchen cabinets and I think it turned out nicely - our house is very dark and sits on a wooded lot in northern Wisconsin so we have a major natural light shortage! I really wanted something bright in there. Hope that helps! The color on the wall is BM Bone White. I can scrounge up some more pics of the Decorator's White next to other BM colors in other rooms of my house if you are interested. :)

We are buying house in FL--south of Sarasota--that we have not seen in person...it is next door to our daughter...She is friendly with the couple who own it...we know the neighborhood pretty well since she has lived there 4 years. When it went up for sale, she did the tour with realtor we used last summer when we were looking for a house in her area...We didn't really have time to go because we knew it would move quickly...even in FL...

This is a typical 70s ranch--2070 sq ft
4/2/2 with 8 ft ceilings,original baths but other aspects have been improved...like a new tile roof, new PEX plumbing, kitchen redone...

We anticipate closing middle of May--
we want to get bids to paint the interior (walls/ceilings/trim) as soon as we can get the keys although we won't be there for long vacation until later in summer...

We know we will have to remodel the two baths later but they are functional and house has been well-maintained by current owners who did the kitchen remodel about 2 yrs ago...

Eventhough they are an older gay couple, they really seem to lack stereotypical design skills...there are 4 different types of flooring--including some of the original vinyl floors in couple of rooms...

We want to paint interior all white--and add color with fabrics/rugs/accessories...
maybe paint accent walls in couple of bedrooms but we can do that later...

Is it foolish to think I can get a jump on color choice by getting some foam boards painted and shipped to my daughter's so they will be there to look at after we close and can see them with light values in different rooms at different times?

I find that looking at rooms online to make color decisions is almost worthless because everyone's home has different light values and monitors aren't always set correctly...

Any suggestions for a nice true white with good opacity--some of their walls are a beige/tan and a blue sponge effect...
The flooring will make a difference in some of the rooms too--since some is lighter oak laminate and some has weathered/driftwood look...

We will use coordinating white for trim...probably Satin
we will paint ceilings flat probably same as walls but maybe a little lighter...
I am used to 10 ft in the house we have in DFW TX area so going to 8 ft ceilings will be little claustrophobic...

loves2read, you will probably get more answers if you start your own post for your own questions.

melinda24, I recently used BM Simply white for all my trim, doors and ceilings. Very happy with the color. Make sure you pick up the slightly larger individual chips they have at the BM store. They have most of the whites and it is so much easier to compare them with the larger chips.