Before you finalize your meta magic feat selection, might I point something out?
Quickened Haste (3+4 = 7), Disintegrate x 2 (2) is well within your reach.
Makes for a nasty first strike ability.
Look over the Permanancy spell. You might want to start play with a Permananent See Invisible or similiar effect.
As for items, here are some things to consider:
There is errata on the price of Boots of Striding and Springing. Look on the WotC site for information, they cost a lot more now.
Boccoms' Blessed Book: The cost to scribe spells can be rather hefty. Copying spells into this spellbook is free.
Major Cloak of Displacement: Against a CR13 monster, you are going to have a tough time getting AC high enough to cause them to miss 50% of the time. Go for a more moderate AC and take this item.
Pearl of Power: 2nd level. This is the level all of the buffing spells are at. Since it takes a standard action to use the PoP, it isn't much use with direct combat spells. Using it for buffing spells still works great, same for any other spell that lasts for a long time. Another good choice is using a 3rd level PoP for Greater Magic Weapon.
Headband of Intellect +6: There should be no question that this is worth every penny. You will get more bonus spells (one at each of 2-4 and 6-8 when comparing 20 vs. 26), three higher DC to resist your spells, and more skill points per level.
Ring of Evasion could be a life saver if you think that you will be able to make the Reflex save. Can change things from Save and Die to Save or Die.
Heward's Handy Haversack is probably the most useful minor item you can find. Definately makes it easier to carry the stuff you want to have. An alternative is the Belt of Many Pockets from Tome & Blood. Yet another option is the Portable Hole, although it isn't nearly as convenient for getting items out as the other two.
Vest of Resistance (also from Tome & Blood) would allow you to pump up your saves while still using the Cloak of Displacement.
Goggles of Night are very nice for a human, although you could just use a Permanancy spell for Darkvision to achieve this.
The MetaMagic Rods from Tome & Blood are worth considering, although I'm not sure they are worth the cost.