I think honestly power conditioning as lowrider mentions is not going to be your best budget spending option and you should really focus on the bigger improvements for your system at the level you are now. before spending $1000's on power conditioning. mind you, you should have some basic filter and surge protection. but that's easily done for under $100.
you'd have to invest $500 and up to get into vacuum / sonic cleaner and still need to buy the towels or vacuum (if sonic) to dry them after. the spin clean is actually very good start I use one myself for quick cleaning.
really you have a $89 cart that's your weakest point IMO then phono stage and pre-power. A better cart will track better, give you more detail give you better pop and tick smoothing and better over all musicality.
I recently looked for a temporary phono stage in the $500 range and found the ifi iphono2 to be one of the best for the money, good place to start looking anyway $499ish. if your thinking of replacing your pre-power then don't spend the money on a separate phono stage now and get one built in to the preamp- integrated- etc.
I mean we can talk room treatments, power conditioning, etc. but you need to work on the basics first then move into the finer details as experience and funds come available. That said there are a few room treatment things you can do for next to no money. for headphones room treatment is a non issue of course unless you can treat your ear canals but I digress.