Oh my god. "You wont need another filter"... I dont care what anybody says... get dual filters. Like mentioned before - If one fails, at least you have a back-up (another one to keep the tank running till you can fix/restart/replace it).
An FX5 is an awesome filter, but I would not run ONLY that. Those and the new G-series fluvals are the only decent fluvals in my opinion and experience (I have a lot of friends who use these and trash the normal units, and I also do tank maintenance for a company and have seen all types of filters first hand over years). You will be better off with 1 FX5 (but please run at least a couple sponge filters with it, or a hang on back)... than you would be with a couple 305's or anything like that.
Eheims ARE terrific filters, they are well-designed, and much less likely to break than anything out there, and VERY few people dislike them. The only downside to them is cost usually, but (That gentlemen who's username I cant remember) suggested you should be able to get some for a price similar to a Rena... I'd do it! Rena's sometimes have problems sealing the head to the unit (XP-3 or 4)... its not often, but it friggen sucks when that happens because the clips on the heads are not as strong as on a fluval or eheim. They are still great filters and I would go with one of those over a 305/405 anyday. Plus the hoses and outputs are much better made and the filters are SUPER simple to clean and unlikely to crack.
Eheim is also VERY VERY quiet... one thing they are well known for, and use very little power (though I have not compared cannister filters in particular)... but I know eheim makes good pumps.
I wont comment on the fish choices, but I have to agree that the tank will be overstocked. Glad you chose to remove the oscar and some of the other fish. It will definitely help you out.
Also those fish prices, I agree, are crap. There is no way you should be paying near $100 for any of those fish on that list! Try somewhere else. Your friend is not helping you out, sorry to say. Plus a "$50" friend fee? wtf is that? Lol. You are a customer, stores should order things for there customers... deals should be even better for friends.
*I just read, you said you can probably afford the FX5 and the Eheim? If so... Do that up. You WILL NOT regret it! I think everyone on this forum can agree that at least 1 of those filters will be a good choice... (even if they dont like the other).. So yeah. Try for the FX5 and something else... even if you cant afford an Eheim or Rena to go with it... maybe get an Aquaclear AC-110 HOB. That will help, but the others will do better. And definitely boot up the 5 bucks, go to a cheap asian fish store (like with ripped-off equipment and stuff) and pick yourself up a $5 sponge filter, just as a back up and have it running all the time.
Hope that helps,
Cheers,
Chris
(Sorry my post is long and disorganized... Its late and things came to mind out of order).