I now own 2074 selections on DVD and VHS, and 483 of them are episodes of TV shows made 1955 (Britain's "Robin Hood") to 2012 ("Nikita" season 2), and I do own all of the sets you list. They are 83 of the 483! I add that I found the first season of "Nikita" for $15, the second season of it for $40 and "Birds Of Prey" for $10, all at local Wal-Marts, so check these stores in the city where you live and the ones nearby. The store near the local Mall got the new "Nikita" weeks before the one nearest me did. I too saw it for $53 at Books-A-Million, and the first season costs $55 there. I bought both for that price at Wal-Mart, and so can you. I buy some DVDs from amazon.com and ebay, so check them and compare prices with local Wal-Marts. I just checked, and ebay has season 2 of Nikita for starting bids of $0.99 and up with several under $10. Amazon has it for $20. Amazon also has the complete series of 24 episodes of "Witchblade" for $16.49 and all 14 episodes of "Birds of Prey" for $12.70.
I like all of these TV shows, so it's hard to choose which to buy first. With luck, you probably can buy all of them at Wal-Mart, amazon.com and/or ebay for the price you expected to pay for only one at a bookstore. Wal-Mart has the best deal on "Birds Of Prey" so far. Ebay is best for "Nikita" season 2. I forgot the price of "Witchblade" at Wal-Mart, so check on it before you buy. 1/12/13 UPDATE- I just checked Wal-Mart, and "Witchblade" costs $13 there.
If I must choose, "Nikita" in my favorite. 1/2 Irish-Polish and 1/2 Vietnamese Margaret Denise Quigley (Maggie Q) and Lyndsy Fonseca are attractive ladies, so I love to see them, and the stories are the most consistently interesting of the series you list. Xander Berkeley is a hissable villain as usual. BUY IT AT EBAY!
"Birds Of Prey" is next by a slight margin. You forgot that Rachel Skarsten is Dinah in it. She's new to me, but I've seen Ashley Scott ("Into The Blue") and Dina Meyer ("Starship Troopers", "Johnny Mnemonic") before. It's too bad this series wasn't on longer. BUY IT AT WAL-MART!
Last on my list is "Witchblade" that's entertaining but more flawed than the others you chose. The sequence of events is disjointed, shall I say, with Sara Pezzini reliving the first half or so of the story in the second half of the series. Will Yune Lee as her partner who was killed returns to life in the new time line. I don't like such overly-contrived plots with weak excuses for strange happenings. I try to do much better in novels I write. BUY IT AT EBAY!
Someone suggested consideration of "Alias" a 2001-2006 TV series starring Jennifer Garner. I liked it well enough, so put it on your list. At amazon.com, the complete series starts at $140. Ebay has three sets of the complete series priced $45, $81 and $90. I haven't seen it at Wal-Mart. BUY IT AT EBAY!
Ebay is your best bet for buying "Nikita" season 2, "Witchblade" and "Alias', but Wal-Mart is best for buying "Birds of Prey".
I've seen on your profile that you are a strong and formidable lady martial artist. You might like "Xena the Warrior Princess" series starring Lucy Lawless. I don't, but you might. The complete series costs $100 or $130 at amazon.com. Ebay doesn't have the complete series, but it has several seaons of it for different prices. I saw it at Wal-Mart, but I don't remember its price.
You might also like the "Wonderwoman" series starring Lynda Carter. The full series costs $56 at amazon.com, but I couldn't find it on ebay, and I haven't seen it at Wal-Mart.