The chips as mentioned where not devices to make vampires, but devices to track them. The bulk of the force in the invasion were ghouls.
Vampires gain fantastic power each time they drink the blood to death of a person, but the more human they are (like in the White Wolf Vampire world) the weaker they are and they have an upper limit on thier power. Alucard being pretty close to the original Vampire (I'd imagine) and having drunk crap loads of people to death is virtualy immortal with his powers unlocked. Celes, being sired by Alucard is also pretty close to the source, meaning that once she does drink someone to death, she really kicks ass.