Honestly, I'd recommend against it. Or rather - I'd recommend starting with the NPC creation rules, and then adding any extra elements you desire from there. Using the PC creation rules will result in enemies with slightly lower hp and vastly overcharged damage output compared to most monsters. Additionally, since you are gearing them up with actual loot instead of the NPC rules, will result in the PCs gaining more cash from the one fight then they would from several levels of adventuring (unless you actively undergear them to compensate, at which case they will have inappropriately weak defenses and attack rolls.)
Now, note that when I am talking about the NPC creation rules, I'm not talking about the class templates - the DMG actually has rules for building NPCs from the ground up, on pages 187-188. The main differences between them and PC creation are as follows:
1) No feats, Paragon Path, or Epic Destinies.
2) 1/2 to 1/3 the number of Encounter, Daily and Utility Powers.
3) Uses the NPC Level Bonus instead of dealing with purchasing magical equipment.
4) Has fewer healing surges, but more base hitpoints. Thus, unlikely to draw out a fight through extended healing, but lack of healing doesn't make it super-fragile.
Now, changes 2, 3 and 4 are mainly there for balance reasons - to keep them at the right level of challenge for the party, rather than able to burn three Daily powers and nuke everything in their way. (Since, as NPCs,
they don't have to worry about conserving powers for later fights.) Also, cutting down on options removes the complexity of running them - five or six options per enemy is manageable for a DM running five NPCs. Fifteen to Twenty options each is much, much more difficulty.
Change number 1, on the other hand, is there to simply reduce the paperwork - remove the need to hunt down seventeen feats and give them a dozen conditional fiddly little bonuses that are unlikely to be worth the effort it took to select them.
With all that in mind, then... my advice, for what you are looking for, is to build NPCs using these rules... and then add a few specific elements to personalize them. You don't need to pick feats for these guys - but if one or two specific feats will really match the NPCs character, add it in. You want the Fighter wielding a Bastard Sword, then go ahead and say they have proficiency with it. Etc. I'd avoid flat numerical feats (Weapon Focus, Armor Specialization, etc), since those are theoretically accounted for with the NPC Bonus - but anything else, you can just hand out as appropriate.
Similarly, if it fits, select a Paragon Path, or maybe parts of one that will stand out the best. Same for Epic Destiny, and so forth. You'll want to be careful - some of these offer very powerful abilities to keep an eye on - but if there is something you feel is character-defining, than you can just go ahead and give it to them.
If you want to have one or two specific magic items used in this NPC party, consider it a reward for the encounter, and then give the item to whomever you want to use it (keeping in mind the Magic Threshold for NPCs) - a Flaming Longsword +2 won't give a bonus to hit or damage for a level 11 character... but it will let them do bonus damage on a crit, turn their weapon into fire, and once during the fight set a PC on fire. Which is really the important part.
So yeah - I highly recommend using the normal NPC rules, and then adding any specific details you feel would truly fit the character. (Basically, the same as James recommends above).
I super-super-super discourage having NPCs with multiple Daily powers, which the system is not designed to throw at PCs. I mean, it might work out fine... but the potential for it to go poorly does worry me. Even with normal NPCs, the powers they are using are often stronger than most enemies, and can make for a more challenging battle than expected.
If you do design some PCs using the normal rules, there really isn't any set way to calculate what they count as, xp wise. They have the damage output of an Elite but the hp of a normal enemy. The best suggestion I can give is just to count it as a monster of a few levels higher than it actually is... but again, I recommend avoiding the situation entirely. There really is nothing you gain from using the PC rules, rather than the NPC rules with a few adjustments to suit any specific elements you feel the NPCs are missing.
