The Blightsteel Colossus is very mana-expensive to be effective (with hardcast) in an aggro/pump/infect deck and with only 2 Quicksilver Amulet and no card draw it will be extremely unlucky to get this beast out.
So instead of these three cards you can play three Phyrexian Crusaders, also improving your mana curve!
Caged Sun at the cost of six mana is not very helpful, also considering you have many artifacts that will not get the +1/+1 (as colorless). Why not to replace it with something that will work better and faster for you? I talk about Overrun, Giant Growth, Livewire Lash (which will be great for your opponent's targeted removals and your targeted pumps! +2 poison counters with every spell!).
One Diabolic Tutor at four mana is not that helpfull. It would be better if you replace him with one of the last mentioned spells above.
Spinebiters are expensive and have to stay one round in play before they show their power, so i would advise against them since you can replace these two with more helpful cards like some more Hand of the Praetors and/or Plague Stinger or even one/two of the four cards i suggested above.
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