poolful

hi all looking for some help i bought a house with a pool need i say more well the heater is bad so the insurance co checked it out and it is, so i neeed to get another, at the sametime i want to replace the filter, witch is a 23 cartrage piece of junk i want to replace the heater with a 400,000 btu and a de filter my pool is 36' long kindey shape 15' and 18' wide in so cal so my quistion is what is the best heater to buy and filter and should i buy the same brand