Do you intend to have it converted at a later date ?
Which model is a very difficult question as we all have our favourites for a variety of reasons.
With your budget, you will probably be looking at what is known as a Gen 1 facelift model. 2005 to mid 2008.
You may be able to get an Gen 2 model, but prices for all Alphard, and Vellfire, model are increasing as their popularity soars.
Location of a competent mechanic is key whatever model you decide on. IMHO, this is especially vital if you opt for a Hybrid.
Most Toyota Dealerships will not work on grey imports.
Some will, most won't.
If buying privately, I would recommend an AA or RAC type inspection for piece of mind.
If from a dealer, make sure you understand any limits within the warranty.
Good Luck, but you are not likely to need it as these are great vehicles.